Earthlink outgoing mail will not send from Mac - VPN issue

I have recently been unable to send email from any Mac email client using Earthlink's SMTP Server. I tried Apple mail, Outlook, eM Client. No problems receiving mail (POP or IMAP) or using web mail client. After some research, I found a tip to turn off VPN. This worked for me. To be specific, AdGuard, which I installed about two weeks ago, will prevent any Mac email client from connecting to Earthlink's SMTP server. If it is in the menu bar, the SMTP connection to Earthlink will not work. Quitting AdGuard and restarting the email client allows the connection to go through normally. TailScale (Mesh VPN) does not cause the same problem. I have not tested any other VPN's. I hope this is useful to someone.

abromber