Comment 58 for bug 1899485

I just tried to reproduce this on my Linux Mint VM (which coxmatthew indicated he experienced the bug on), using a new profile created using TB 45.8 and opened using a clean install of TB 52.2.1.

I added the line in prefs.js setting ldap_2.servers.history.filename to "test.mab" and then connecting to my Office365 account using davmail, and replying to an email that was sent from an address that is NOT in any of my address books, and the mail sent exactly as expected.

The only thing that didn't "work" is that the address didn't get added to test.mab, because "mail.collect_addressbook" wasn't set in prefs.js, so the default value of "moz-abmdbdirectory://history.mab" was used. Once I set mail.collect_addressbook to "moz-abmdbdirectory://test.mab", even the addition of the email address to the address book worked exactly as expected.

My hunch is that there is more at play here than just that one preference setting.