So I have 4 accounts setup on Outlook. 3 of them work perfectly. 1 of them won't send any emails. I have received two separate error messages and exhausted myself checking for assistance through Microsoft and waiting in a queue for half an hour for Yahoo's internet support.

So. Please help! 

I am connecting through port 25 for outgoing mail and I have verified 10x that the settings are correct for my account. I can receive 100% of the mail but can't SEND any of it.

Here are the error messages I'm receiving:

Unable to logon to the server using Secure Password Authentication. Account: 'email@domain.com', Server: 'mail.domain.com', Protocol: POP3, Server Response: '-ERR Unsupported authentication mechanism.', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC18

[the one below is when I uncheck that "Secure PW Authent" box, because, really, I have no clue what else to try]

Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: 'email@domain.com', Server: 'mail.domain.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 10053, Error Number: 0x800CCC0F


AT&T/Yahoo's website suggested I try port 587 but that didn't do anything either. I've closed out Outlook, deleted the email account and then recreated it, and done just about everything possible. 

Yep, got this error for that one:

"The connection to the server has failed. Account: 'email@domain.com', Server: 'mail.domain.com', Protocol: SMTP, Port: 26, Secure(SSL): No, Socket Error: 10060, Error Number: 0x800CCC0E"

I have a great collection of error messages tho. 

LOL Yes, if I wasn't putting in my actual domain, I'd hope someone here would slap me.

Error message for changing the outgoing server:

"Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: 'email@domain.com', Server: 'domain.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 10053, Error Number: 0x800CCC0F"

Good ole error 0x800CCC0F. 

I'm attempting some fixes with deleting the outbox (siiiiigh) and using one of Yahoo/AT&T's tools to check my machine.