I am unable to send an email from any of my Virgin emails addresses (ntlworld.com & virginmedia.com), on my virgin cable broadband connection.
Thunderbird error console shows
mailnews.smtp: Command failed: 525 Authentication Denied (VM305); currentAction=_actionAUTHComplete SmtpClient.jsm:514:19
mailnews.smtp: Authentication failed: Authentication Denied (VM305)
But if I switch my laptop wifi connection over to my mobile hotspot, then the email sends okay.
The same happens from my mobile if I switch from my VM WiFi, onto mobile data.
I can receive fine on the accounts on all connections, so I know there are NO password/account locked type of issues.
It seems to be a trust issue between internal parts of Virginmedia own network!