User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:80.0) Gecko/20100101 Firefox/80.0

Steps to reproduce:

I tried to send a message to a mail list (team members).
These addresses are expanded by the companies MTA to cover the members of a team - they are not local mail address lists in the Thunderbird address book.
The mails to those lists are meant to be collected and thus sending to the expanded list (all member mail addresses) is not identical.

Actual results:

No PGP key was assigned to this recipient and I could not assign the list of PGP keys for the known members of that team.

Expected results:

With Enigmail it was possible to assign a list of PGP keys to a mail address (in this case an address that gets expanded to multiple recipients by the MTA).

Maintenance of this mapping was in the responsibility of each individual sender to that list. The PGP keys could be mapped via the address book if a mail list could have members (with their associated PGP keys) but mails to that list were not expanded when sending - the mail list name was kept as the To (or CC) address when handing out the message to the MTA.

I.e. this would require an additional flag "do not expand" for mail lists, but with the PGP keys selection using the member information to control the encryption.

I consider this change in behavior as a defect since it causes long practiced processes to fail and is a severe regression relative to Thunderbird+Enigmail.

Regarding the title of this bug report: The mail list is local to the organization, not the sending device, in the use case I care about ...

This feature request is currently tracked in bug 1644085.