For historical reasons, my Virgin Media account is set up with a username on my own domain - say firstname.lastname@example.org. Because that domain doesn't appear to allow me to edit the SPF record, I can no longer use Virgin Media to send emails from email@example.com, although I can of course use it to receive emails sent to that address, given that I set up mail forwarding correctly. This hasn't been a problem until I tried to set up the account up Outlook in Microsoft 365. The issue is that the setup process does not appear to allow for a username that isn't the same as the related email address, which means that if I use firstname.lastname@example.org, the in principle MS 365 should be able to log on but won't be able to send its test email, while if I use my VM address, say email@example.com, then it can't log on, although if it had done so it could then send and receive emails. I'm looking for a way out of this - either to change my VM logon username to be my VM email address, or to set different username and email addresses within Microsoft 365. Can anyone help, please?
OK, this is really weird. I tried once more to set the account up, using my VM email address, and it seems to have worked. If I look under "server settings", it (unsurprisingly!) shows the VM email address as my username. If I try to login to webmail with that username, it fails, and if I try to change the username in Outlook to the one I know to be correct - which is possible now that the account has been set up - that fails. How is this possible? On both iPhone mail and Thunderbird the account uses the expected username.