I cannot send emails via SMTP on third-party software

Hi.

When I log in to my account via a third-party software, in this case Thunderbird, I cannot send emails via SMTP.

I can receive emails, so I know the IMAP is well configured. Sending emails also works on the web. It's just a SMTP problem.

For SMTP, I tried both:

• smtp-mail.outlook.com, port 587, STARTTLS, Oauth2
  • As documented here: https://support.microsoft.com/en-us/office/pop-imap-and-smtp-settings-for-outlook-com-d088b986-291d-42b8-9564-9c414e2aa040
• smtp.office365.com, port 587, STARTTLS, Oauth2
  • which is a configuration I found in the forums.

I have a personal subscription, so I don't know which would apply. In any case, none of them work. I always get a SMTP authentication error.

I tried removing and adding the account again, to no avail. This happens in 2 different PCs.

Note: this email account is a legacy account ending in @netcabo.pt, which used to be email accounts provided by a Portuguese ISP, back in the day. Nowadays, they are Microsoft/Outlook email accounts, keeping the domain.