How to send mail to several people from one email?

Question

Mail server

Good afternoon guys. I wanted to do something like this. There is an external mailer. It contains addresses from which people send letters. These addresses are linked to departments. Actually what is the point. I want to install a local Zimbra server, bind it to LDAP accounts. Next, I want to fetch mail from external mail addresses using fetchmail and send mail to the mailing list, which will contain LDAP accounts, respectively. This is all good and understandable. And how to make people from the same mailing list send letters, and they go through an external mail server, that is, they are sent from under the same email address of the external server.
Short example:
For example, the accounting department has [email protected] - this is an external address
[email protected] - this is a general mailing list to which all letters will be sent, from [email protected]
AND all people who were members of [email protected] ([email protected], [email protected], [email protected] .domain) when sending mail to example.gmail.com, for example, had an external address [email protected]
Tell me where to dig?)

Answer 1

If on the sendmail mailer, then towards virtusertable or the like. If there is no such functionality - in the direction of libmilter, if you really want to get confused :)