Question: i want to override the default finisher for forms system extension of TYPO3 to set multiple email addresses for recipient address
or adding a new field for more email recipients

the problem is, that multiple email adresses in the recipient address field are running into an ecception

> 
> Address in mailbox given
>  [first@email.de,second@email.de] does not comply with
>  RFC 2822, 3.6.2.
> 
> 
> 

I know, I can use the recipients email and one cc, so I got 2 email recipients, but I need more ;)

like this:

> 
> mail1,mail2,mail3,…
> 
> 
> 

thanks for help or links to get this done

Answer: 
I found the issue :(
it's explained here:
[Use a SQL Server database in a UWP app](https://learn.microsoft.com/en-us/windows/uwp/data-access/sql-server-databases)

in the section: **Trouble connecting to your database?**

The TCP/IP protocol is disabled by default and **must be enabled**.
Now how is it possible that the same app in WPF works, that VS2019 is able to connect (not to mention the SSMS...) and only the UWP does not connect is a mystery for me... but now it works!
UWP apps don't have network access by default. See:

> 
> Capabilities 
> 
> 
> In order to use networking, you must add appropriate
>  capability elements to your app manifest. If no network capability is
>  specified in your app's manifest, your app will have no networking
>  capability, and any attempt to connect to the network will fail.
> 
> 
> 

[Networking basics - UWP applications](https://learn.microsoft.com/en-us/windows/uwp/networking/networking-basics)