SMTP server fails to recognize username
My 95-year old parents have an iMac 21.5-inch 2.7GHz Quad-Core Intel Core i5 using 10.8.5 which they love and use daily for email, and iTunes. (Dad is the last remaining band member of a famous 1941 swing band that made the first music videos for the Panorams!)
All of a sudden, the SMTP server will not recognize Dad's username and no mail would send.
I discovered this because Dad was trying to send an email which would not send, so he left it, and the error message on the screen. (LOL) I saw that he had entered a mal-formed email, so I fixed that and it flew off fine.
I then went into his Previous Recipients tab and cleared up all his 'mistakes' to lessen the chance of that happening again.
But when I attempted to forward an email to myself from his account to mine, it would not send. Nothing would send, and the message was that his username was being rejected but ONLY by the SMTP server.
After confirming via webmail that his account was working for both send and receive, I thought perhaps the preferences had become corrupted. The disk checked out OK and I ran permissions until clean. No problems there, so I deleted and set up the acct again with no success.
Eventually I got the SMTP to work by using the obscure code for the email account that Verizon uses (something that looks like vzeXXXX@verizon.net) instead of his username@verizon.net in the preferences for the outgoing server.
Now the question remains, the tech and I could not decide whether VZ's server is messed up, as it just stopped working for no reason, or is the Mail.app at fault?
These techs work from a script, and have no idea what a POP acct or 5.1.1 error is, mind you.
iMac, OS X Mountain Lion (10.8.5)