our deferred revenue at the end of 2020 was $ 41.5 million , compared with $ 43.3 million at the end of 2019. we generated cash flows from operations of $ 31.3 million during fiscal 2020. our cash and cash equivalents were $ 21.4 million at the end of 2020 , compared with $ 13.3 million at the end of 2019. our services are sold on a subscription basis with contract terms historically ranging from one to five years billed annually . we are increasingly moving toward a monthly billing model . this shift has been largely driven by our recent acquisition activity . we recognize revenue ratably on a monthly basis over the term of the subscription once service commences . 29 we attempt to grow our business by signing new customers to subscription services and or selling new or higher volume services to existing customers ( i.e . , “ upsell ” ) while retaining existing customers through renewal of their subscriptions for successive periods . our backlog consists of the total order value of contracted business that has not yet been recognized into revenue . backlog is calculated by adding to the existing contracted order value the total value of all orders booked in the period ( e.g . , quarterly ) less the value of revenue recognized for that period . although orders historically have been non-cancellable , occasionally we adjust backlog for customer bankruptcy or change of term , but these instances are rare and do not materially impact the backlog amount . the backlog will grow if the value of total orders added in a period exceeds the value of revenue recognized in that period . conversely , the backlog amount will decline if revenue recognized exceeds the total order value added for the period . a decline in backlog may result from fluctuations in total orders caused by timing of renewal orders or by the shortening of the average term of our contracts from a multi-year to an annual commitment or to a monthly billing and subscription model . as of december 31 , 2020 , our net dollar customer retention percentage was 100 % . we calculate this percentage by first identifying our current period renewal and upsell orders secured from existing customers and then combining these totals with billings for the period . we then compare this amount to the total orders that were due to renew and were then combined with scheduled billings . increasing retention is a key driver for the company to increase overall revenue and annual recurring revenue . deferred revenue is the value of contracted business that has been paid but has not been recognized as revenue . see description of the components of the backlog following in “ results of operations - backlog ” in this “ item 7 , management 's discussion and analysis of financial condition and results of operations . ” as of december 31 , 2020 , our annual recurring revenue ( arr ) was $ 237.7 million . we calculate arr by determining the annual or monthly revenue of subscription agreements that are active as of the end of the applicable period and multiplying by 1 or 12 depending on the term of such agreements . we monitor this metric to aid in determining to what extent individual customer relationships , considered in the aggregate , are growing or declining in financial magnitude . our operations and future prospects are further discussed throughout this “ item 7. management 's discussion and analysis of financial condition and results of operations . ” there are no assurances we will be successful in our efforts to achieve continued growth . our continued growth depends on the timely development and market acceptance of our products and services . see “ item 1a . risk factors ” for more information on the risks relative to our operations and future prospects . critical accounting policies and estimates in preparing our consolidated financial statements , we make estimates , assumptions and judgments that can have a significant impact on revenue , income from operations and net income , as well as the value of certain assets and liabilities on our consolidated balance sheet . the application of our critical accounting policies requires an evaluation of a number of complex criteria and significant accounting judgements by us . management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances ( including but not limited to the potential impacts arising from the recent covid-19 pandemic and public and private sector policies and initiatives aimed at reducing its transmission ) , the results of which form the basis for making judgements about the carrying values of assets and liabilities . we evaluate our estimates on a regular basis and make changes accordingly . senior management has discussed the development , selection and disclosure of these estimates with the audit committee of our board of directors . actual results may materially differ from these estimates under different assumptions or conditions . if actual results were to materially differ from these estimates , the resulting changes could have a material adverse effect on our consolidated financial statements . we consider accounting policies to be critical when they require us to make assumptions about matters that are highly uncertain at the time the accounting estimate is made and when different estimates that our management reasonably has used have a material effect on the presentation of our financial condition , changes in financial condition or results of operations . management believes the following critical accounting policies reflect our more significant estimates and assumptions used in the preparation of our consolidated financial statements . story_separator_special_tag net income ( loss ) for 2020 was $ ( 6.4 ) million in 2020 compared with $ ( 14.6 ) million in 2019 and $ 15.4 million in 2018. the year-over-year improvement in our net loss was primarily due to revenue growth and the completion of prior year acquisition and integration related costs associated with our appriver purchase , as well as cost reductions in response to the covid-19 pandemic . our 2019 net loss is attributed to significant transaction and integration-related costs incurred to acquire appriver and deliveryslip in 2019 , amortization of intangible assets recognized from the same acquisitions as well as higher operating expenses and interest expense . our 2018 net income includes a $ 7.8 million tax benefit resulting from a decrease to our deferred tax asset valuation allowance based on our expected future profitability and ability to use net operating losses . net income ( loss ) attributable to common shareholders for 2020 was $ ( 15.5 ) million compared with $ ( 24.6 ) million in 2019 and $ 15.4 million in 2018. our 2020 and 2019 net loss attributable to common shareholders includes deemed and accrued dividends of $ 9.0 million , and $ 9.9 million , respectively , to preferred shareholders . net income ( loss ) per diluted share was $ ( 0.29 ) for 2020 compared to $ ( 0.46 ) for 2019 and $ 0.29 for 2018. unrestricted cash was $ 21.4 million on december 31 , 2020 . 34 results of operations revenue the following table sets forth a year-over-year comparison of our total revenues : replace_table_token_3_th the $ 45.1 million , or 26 % , increase in revenue in 2020 over 2019 was related in part to recognition of twelve full months in sales for the year ended december 31 , 2020 , attributable to our appriver business acquired in february 2019. the $ 103.0 million or 146 % increase in revenue in 2019 over 2018 was primarily related to our appriver acquisition in february 2019 , which contributed $ 97.8 million for the year-end december 31 , 2019. we additionally grew our revenue for these periods with continued success in our subscription-based business model with both steady additions to the subscriber base and with a high rate of existing customer renewals and the realization of previously contracted revenue in our backlog . in the year ended december 31 , 2020 , excluding our cloudally sales , we categorized our revenue in the following core industry verticals : 21 % healthcare , 17 % financial services , 3 % government sector and 59 % as other . in the year ended december 31 , 2019 , we categorized our revenue in the following core industry verticals : 23 % healthcare , 19 % financial services , 4 % government sector and 54 % as other . additionally , sales continued from a wide base of distributors . approximately 76 % and 74 % of our new business transacted in the year ended december 31 , 2020 and 2019 , respectively , resulted from our partner relationships . while we have continued to add new bundled price offerings to our product portfolio , our list pricing has remained generally consistent during the periods shown above . however , there are no assurances that potential increased competition in this market or other factors , including inflation , will not result in future price erosion . price erosion , should it occur , could have a dampening effect on order growth and the revenue derived from our new orders . revenue outlook : we expect continued growth in our existing offering and in our new products , along with increased sales from our partner channels to increase our business in 2021 and increase our year-over-year revenue . annual recurring revenue we measure the health of our subscriber base by the growth of our annual recurring revenue ( “ arr ” ) , which is defined as the aggregate annualized contract value attributable to recurring revenue contracts as of the end of the applicable reporting period . we calculate arr by determining the annual or monthly revenue of subscription agreements that are active as of the end of the applicable period and multiplying by 1 or 12 , depending on the term of such agreements . arr aids us in determining to what extent individual customer relationships , considered in the aggregate , are growing or declining in financial magnitude . arr is summarized in the table below : replace_table_token_4_th backlog our backlog was $ 83.4 million at december 31 , 2020 , compared to $ 89.4 million at december 31 , 2019. the backlog is comprised of contractual commitments that we expect to amortize into revenue . as of december 31 , 2020 , the backlog was comprised of the following elements : $ 41.5 million of deferred revenue that has been billed and paid , $ 12.9 million billed but unpaid , and approximately $ 29.0 million of unbilled contracts . the decline in backlog resulted from the shortening of the average term of our contracts from a multi-year to an annual commitment or to a monthly billing and subscription model . the backlog is recognized into revenue ratably as the services are performed . approximately 75 % of the total backlog is expected to be recognized as revenue during the next twelve months . 35 cost of revenue the following table sets forth a year-over-year comparison of the cost of revenue . replace_table_token_5_th cost of revenues is comprised of microsoft fees mostly associated with the resale of microsoft office365 and hosted exchange products , costs related to operating and maintaining the zixdata center , third party data center costs , a field deployment team , customer service and support , and depreciation expense of computer equipment and amortization of acquired technology . the $ 35.9 million increase in 2020 compared to 2019 reflected in the table above

liquidity and capital resources overview based on our 2020 financial results and current expectations , including our assessment of the covid-19 pandemic potential impact on our company , we believe our cash and cash equivalents , cash generated from operations , and availability under our $ 25 million revolving facility ( which , as of december 31 , 2020 , was repaid in full and the entire undrawn balance of $ 25 million was available to fund working capital and for other general corporate purposes , including the financing of permitted acquisitions , investments and restricted payments , subject to the conditions contained in the credit agreement ) will satisfy our working capital needs , capital expenditures , investment requirements , contractual obligations , commitments , and other liquidity requirements associated with our operations through at least the next twelve months . we plan for and measure our liquidity and capital resources through an annual budgeting process and quarterly reviews , and we will continue to monitor our position to protect our company against uncertainties related to the covid-19 crisis . during 2020 , our cash flow from operations was $ 31.3 million , an increase of $ 17.3 million from the $ 14.0 million cash flow from operations during 2019. at december 31 , 2020 , our cash and cash equivalents totaled $ 21.4 million , an increase of $ 8.1 million from the december 31 , 2019 balance . the $ 8.1 million increase in our cash position is primarily attributable to our improved cash flow from operating activities in 2020 including management actions to reduce spending in response to the covid-19 crisis , as well as from increased spending in the prior year associated with due diligence , banking and other fees associated with our appriver acquisition in february 2019. for the year ended december 31 , 2020 , we achieved 26 % growth in revenue , 48 % gross margin and strong cash collections which increased our cash on hand level after investing back for business integration .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```liquidity and capital resources overview based on our 2020 financial results and current expectations , including our assessment of the covid-19 pandemic potential impact on our company , we believe our cash and cash equivalents , cash generated from operations , and availability under our $ 25 million revolving facility ( which , as of december 31 , 2020 , was repaid in full and the entire undrawn balance of $ 25 million was available to fund working capital and for other general corporate purposes , including the financing of permitted acquisitions , investments and restricted payments , subject to the conditions contained in the credit agreement ) will satisfy our working capital needs , capital expenditures , investment requirements , contractual obligations , commitments , and other liquidity requirements associated with our operations through at least the next twelve months . we plan for and measure our liquidity and capital resources through an annual budgeting process and quarterly reviews , and we will continue to monitor our position to protect our company against uncertainties related to the covid-19 crisis . during 2020 , our cash flow from operations was $ 31.3 million , an increase of $ 17.3 million from the $ 14.0 million cash flow from operations during 2019. at december 31 , 2020 , our cash and cash equivalents totaled $ 21.4 million , an increase of $ 8.1 million from the december 31 , 2019 balance . the $ 8.1 million increase in our cash position is primarily attributable to our improved cash flow from operating activities in 2020 including management actions to reduce spending in response to the covid-19 crisis , as well as from increased spending in the prior year associated with due diligence , banking and other fees associated with our appriver acquisition in february 2019. for the year ended december 31 , 2020 , we achieved 26 % growth in revenue , 48 % gross margin and strong cash collections which increased our cash on hand level after investing back for business integration .
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 Suspicious Activity Report : our deferred revenue at the end of 2020 was $ 41.5 million , compared with $ 43.3 million at the end of 2019. we generated cash flows from operations of $ 31.3 million during fiscal 2020. our cash and cash equivalents were $ 21.4 million at the end of 2020 , compared with $ 13.3 million at the end of 2019. our services are sold on a subscription basis with contract terms historically ranging from one to five years billed annually . we are increasingly moving toward a monthly billing model . this shift has been largely driven by our recent acquisition activity . we recognize revenue ratably on a monthly basis over the term of the subscription once service commences . 29 we attempt to grow our business by signing new customers to subscription services and or selling new or higher volume services to existing customers ( i.e . , “ upsell ” ) while retaining existing customers through renewal of their subscriptions for successive periods . our backlog consists of the total order value of contracted business that has not yet been recognized into revenue . backlog is calculated by adding to the existing contracted order value the total value of all orders booked in the period ( e.g . , quarterly ) less the value of revenue recognized for that period . although orders historically have been non-cancellable , occasionally we adjust backlog for customer bankruptcy or change of term , but these instances are rare and do not materially impact the backlog amount . the backlog will grow if the value of total orders added in a period exceeds the value of revenue recognized in that period . conversely , the backlog amount will decline if revenue recognized exceeds the total order value added for the period . a decline in backlog may result from fluctuations in total orders caused by timing of renewal orders or by the shortening of the average term of our contracts from a multi-year to an annual commitment or to a monthly billing and subscription model . as of december 31 , 2020 , our net dollar customer retention percentage was 100 % . we calculate this percentage by first identifying our current period renewal and upsell orders secured from existing customers and then combining these totals with billings for the period . we then compare this amount to the total orders that were due to renew and were then combined with scheduled billings . increasing retention is a key driver for the company to increase overall revenue and annual recurring revenue . deferred revenue is the value of contracted business that has been paid but has not been recognized as revenue . see description of the components of the backlog following in “ results of operations - backlog ” in this “ item 7 , management 's discussion and analysis of financial condition and results of operations . ” as of december 31 , 2020 , our annual recurring revenue ( arr ) was $ 237.7 million . we calculate arr by determining the annual or monthly revenue of subscription agreements that are active as of the end of the applicable period and multiplying by 1 or 12 depending on the term of such agreements . we monitor this metric to aid in determining to what extent individual customer relationships , considered in the aggregate , are growing or declining in financial magnitude . our operations and future prospects are further discussed throughout this “ item 7. management 's discussion and analysis of financial condition and results of operations . ” there are no assurances we will be successful in our efforts to achieve continued growth . our continued growth depends on the timely development and market acceptance of our products and services . see “ item 1a . risk factors ” for more information on the risks relative to our operations and future prospects . critical accounting policies and estimates in preparing our consolidated financial statements , we make estimates , assumptions and judgments that can have a significant impact on revenue , income from operations and net income , as well as the value of certain assets and liabilities on our consolidated balance sheet . the application of our critical accounting policies requires an evaluation of a number of complex criteria and significant accounting judgements by us . management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances ( including but not limited to the potential impacts arising from the recent covid-19 pandemic and public and private sector policies and initiatives aimed at reducing its transmission ) , the results of which form the basis for making judgements about the carrying values of assets and liabilities . we evaluate our estimates on a regular basis and make changes accordingly . senior management has discussed the development , selection and disclosure of these estimates with the audit committee of our board of directors . actual results may materially differ from these estimates under different assumptions or conditions . if actual results were to materially differ from these estimates , the resulting changes could have a material adverse effect on our consolidated financial statements . we consider accounting policies to be critical when they require us to make assumptions about matters that are highly uncertain at the time the accounting estimate is made and when different estimates that our management reasonably has used have a material effect on the presentation of our financial condition , changes in financial condition or results of operations . management believes the following critical accounting policies reflect our more significant estimates and assumptions used in the preparation of our consolidated financial statements . story_separator_special_tag net income ( loss ) for 2020 was $ ( 6.4 ) million in 2020 compared with $ ( 14.6 ) million in 2019 and $ 15.4 million in 2018. the year-over-year improvement in our net loss was primarily due to revenue growth and the completion of prior year acquisition and integration related costs associated with our appriver purchase , as well as cost reductions in response to the covid-19 pandemic . our 2019 net loss is attributed to significant transaction and integration-related costs incurred to acquire appriver and deliveryslip in 2019 , amortization of intangible assets recognized from the same acquisitions as well as higher operating expenses and interest expense . our 2018 net income includes a $ 7.8 million tax benefit resulting from a decrease to our deferred tax asset valuation allowance based on our expected future profitability and ability to use net operating losses . net income ( loss ) attributable to common shareholders for 2020 was $ ( 15.5 ) million compared with $ ( 24.6 ) million in 2019 and $ 15.4 million in 2018. our 2020 and 2019 net loss attributable to common shareholders includes deemed and accrued dividends of $ 9.0 million , and $ 9.9 million , respectively , to preferred shareholders . net income ( loss ) per diluted share was $ ( 0.29 ) for 2020 compared to $ ( 0.46 ) for 2019 and $ 0.29 for 2018. unrestricted cash was $ 21.4 million on december 31 , 2020 . 34 results of operations revenue the following table sets forth a year-over-year comparison of our total revenues : replace_table_token_3_th the $ 45.1 million , or 26 % , increase in revenue in 2020 over 2019 was related in part to recognition of twelve full months in sales for the year ended december 31 , 2020 , attributable to our appriver business acquired in february 2019. the $ 103.0 million or 146 % increase in revenue in 2019 over 2018 was primarily related to our appriver acquisition in february 2019 , which contributed $ 97.8 million for the year-end december 31 , 2019. we additionally grew our revenue for these periods with continued success in our subscription-based business model with both steady additions to the subscriber base and with a high rate of existing customer renewals and the realization of previously contracted revenue in our backlog . in the year ended december 31 , 2020 , excluding our cloudally sales , we categorized our revenue in the following core industry verticals : 21 % healthcare , 17 % financial services , 3 % government sector and 59 % as other . in the year ended december 31 , 2019 , we categorized our revenue in the following core industry verticals : 23 % healthcare , 19 % financial services , 4 % government sector and 54 % as other . additionally , sales continued from a wide base of distributors . approximately 76 % and 74 % of our new business transacted in the year ended december 31 , 2020 and 2019 , respectively , resulted from our partner relationships . while we have continued to add new bundled price offerings to our product portfolio , our list pricing has remained generally consistent during the periods shown above . however , there are no assurances that potential increased competition in this market or other factors , including inflation , will not result in future price erosion . price erosion , should it occur , could have a dampening effect on order growth and the revenue derived from our new orders . revenue outlook : we expect continued growth in our existing offering and in our new products , along with increased sales from our partner channels to increase our business in 2021 and increase our year-over-year revenue . annual recurring revenue we measure the health of our subscriber base by the growth of our annual recurring revenue ( “ arr ” ) , which is defined as the aggregate annualized contract value attributable to recurring revenue contracts as of the end of the applicable reporting period . we calculate arr by determining the annual or monthly revenue of subscription agreements that are active as of the end of the applicable period and multiplying by 1 or 12 , depending on the term of such agreements . arr aids us in determining to what extent individual customer relationships , considered in the aggregate , are growing or declining in financial magnitude . arr is summarized in the table below : replace_table_token_4_th backlog our backlog was $ 83.4 million at december 31 , 2020 , compared to $ 89.4 million at december 31 , 2019. the backlog is comprised of contractual commitments that we expect to amortize into revenue . as of december 31 , 2020 , the backlog was comprised of the following elements : $ 41.5 million of deferred revenue that has been billed and paid , $ 12.9 million billed but unpaid , and approximately $ 29.0 million of unbilled contracts . the decline in backlog resulted from the shortening of the average term of our contracts from a multi-year to an annual commitment or to a monthly billing and subscription model . the backlog is recognized into revenue ratably as the services are performed . approximately 75 % of the total backlog is expected to be recognized as revenue during the next twelve months . 35 cost of revenue the following table sets forth a year-over-year comparison of the cost of revenue . replace_table_token_5_th cost of revenues is comprised of microsoft fees mostly associated with the resale of microsoft office365 and hosted exchange products , costs related to operating and maintaining the zixdata center , third party data center costs , a field deployment team , customer service and support , and depreciation expense of computer equipment and amortization of acquired technology . the $ 35.9 million increase in 2020 compared to 2019 reflected in the table above

