Fleshing out @JFallows' answer a bit...
Email RFCs are a bit opaque to read but your list should comprise comma-delimited (comma, no spaces or line breaks) emails addresses in either of these forms:
Thus as a mailing a list this might look like:
I'll assume you are storing email addresses in $Email (e.g.
firstname.lastname@example.org), and that the name to be used in the first part of the longer form above in $FullName (e.g.
Jane Doe). I'll assume all the notes with such data use the 'Person' prototype and that we've added a String type user attribute $EmailAddrString.
Now our agent uses this query:
$Prototype=="Person" (of course you can refine this query to find only people you want on the list)
The agent's action is:
Lastly the agent's rule is:
The text of your note is now a correctly formatted string you can copy to your email 'to' field - or better the bcc field to keep recipients addresses hidden from each other. IOW , your agent $text will look like this:
Note: the use of a comma only between each address and no line breaks in the list as per the RFCs.