The password and relays had to be reset in GoDaddy.

I'm getting a weird connection error when trying to send messages. 

[*] Connection established to 64.202.165.58
>> 0050 220 smtpauth01.prod.mesa1.secureserver.net ESMTP
<< 0022 EHLO [192.168.1.102]
>> 0044 250-smtpauth01.prod.mesa1.secureserver.net
>> 0022 250-AUTH LOGIN PLAIN
>> 0014 250-8BITMIME
>> 0016 250 PIPELINING
<< 0012 AUTH LOGIN
>> 0018 334 VXNlcm5hbWU6
<< 0038 amVyZW1pYWhfbW9zc0Bjb2JyYWExLmNvbQ==
>> 0018 334 UGFzc3dvcmQ6
<< 0014 SVlrTmtVSHM=
>> 0021 451 Internal error.

Talk to the provider  of your SMTP host, this 451 error looks like he's having some sort on internal problem with the AUTH command.

Just to amplify on Thomas's report a little... It's your ISP's server that is saying "451 Internal error", not Pegasus Mail, and that indicates that it's his server that is having the problem.

Cheers!

-- David --

I have contacted GoDaddy (who I use for email), and they asked for more information, which I gave them, but as of now, there is no resolution with them. I agree this is probably their problem, though.