Config Thunderbird

2025-02-13, Thu

Thunderbird is more useful than the default Mail client comes with macOS, since it functions not only as a mail client, but also newsfeed reader and IRC client. Even considering only mails, there is feature in it that's quite convenient, e.g. identify.

1. Using Identities

In short, Thunderbird identities1 allows selection of different From addresses while sending mail. A default identity will be created when the mail account is created, but extra ones could be added through Tools > Account Settings > [Account Name] > Manage Identities.

Outgoing Server (SMTP) settings like user name and default identity could be changed here as well, which comes handy when a custom domain is used for sending email2.

2. Problem: Unable to send mail through Outlook

While trying to send mail through Outlook account in Thunderbird, I got the following error message:

Login to server smtp.office365.com with username <USERNAME> failed

Online search results aside, this issue could also be caused by alias3 in the Outlook account: it seems like only the primary alias is accepted as valid username of smtp.office365.com.

So when other options all have failed, give this direction a try.

3. Newsfeeds

Footnotes:

1

Thunderbird documentation on Using Identities https://support.mozilla.org/en-US/kb/using-identities

2

When using custom domains, remember to set the SPF, DKIM and DMARC properly in domain name provider. For what these settings are for, search topics like "Gmail spam and authentication"