Members of the Bournemouth e-Panel mailing list, who had signed up to take part in surveys, received an email with all the recipients' addresses visible.
The council apologised and asked recipients to delete the original email which was sent last week.
Service director Richard Saunders said "further investigations" were being carried out to prevent a repetition.
An Information Commissioner's Office spokesman said it was aware of the breach and would be keeping a note on its system.
He said as it was not regarded as significant enough to take further action and the council had followed the recommended procedures following the error.

Sales rose 21% in the third quarter giving the company €723m (£522m) in revenue, a 9% rise from last year.
Fiat Chrysler, which sold 10% of its stake in Ferrari to New York investors last week also released results.
Shares fell 3.5% after it said it made significant losses stemming from what the company called a "recall environment".
The world's 7th largest car company reported a net loss of €299m despite growing sales of Jeeps globally.
Fiat Chrysler did manage to boost earning 35% to €1.3bn from €968m the previous year.
Fiat Chrysler confirmed its revised earnings forecast which it raised at the end of the second quarter.
The sale of Ferrari helped secure this increase.
Ferrari said it expects deliveries to reach 7,700 vehicles by year end.
Hundreds of email addresses have been inadvertently circulated following a mistake by Bournemouth Borough Council.
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Luxury carmaker Ferrari reported a jump in profit in the third quarter boosted by higher sales.