I don't think Pegasus is responsible, but my mail provider refuses to go any further until I have discussed it with you. We have used Pegasus for many years, without problems. We are currently running Pegasus 4.80, on Win-10, and using a mail server from our local internet provider, eastlink.ca. In brief, Eastlink revised their security protocols, requiring us to update our password. The revised p/w works on Eastlink's webmail, but when we entered it into Pegasus, using the Pegasus Setup Wizard, followed by an attempted login to Eastlink, the trace shows things going smoothly up to the request, (from the mail server), for the p/w, at which point their server throws an error message: ERR AUTH, Authentication Failed. (Pegasus displays a message that either username or password are incorrect.)

Seems to me that it is not Pegasus which is complaining, but Eastlink, who are rejecting the transmission from Pegasus. Eastlink says it has nothing to do with them, but must have something to do with the transmission from Pegasus itself. (I don't have a very good feeling about this being easily resolved...) (And, underlying it is a distinct hostility on the part of Eastlink to our use of POP-3 in the first place.)

Look into whether Eastlink has a configuration option that allows you to allow certain apps, Google once called it "allow less secure apps".

Also look into whether they have a function that lets you create a password for a specific program, Google calls it an "app password".

For relevance, what email hosts are doing is moving away from allowing a program to access the hosted account with the same username and password that is used to login to the account with a browser.

Took the better part of a day to track down the problem, but probably worthwhile to record the root cause. (At least I think it was the cause - the problem went away when the extra addresses were deleted. But this wasn't the only change made, so I can't be sure.)

When we went into the SMTP and POP3 details there were a whole raft of addresses listed for each, (mostly correct: mail.eastlink.ca, but multiple instances of same). We deleted all but one, then configured that single entry with the new password. Following this the provider accepted the login and password without difficulty. (Had to do it separately for POP3, which worked fine, but still wouldn't send. Then went to SMTP and again entered username and p/w into the single remaining address. My analysis is that, with the multiple entries for each one, Pegasus was choosing one of what was an old address, (with the old p/w) to login to the server. By removing all but one choice, we ensured that poor Pegasus got the correct (current, new) p/w.

I am glad that you solved the problem. It would have been a tough one to figure out from our recliners.