A while ago, I started having problems sending e-mail from home and had no idea why as I use the mail server located in my office in town (it was never a problem in the past). I could receive mail, but sending just would not work.
I tried everything I knew, changing from pop3 to IMAP, to secure pop3, etc. I was completely stumped as I could remotely watch my mail server connection and see that there was no SMTP for sending mail.
Eventually, I spoke to a senior engineer at Netvigator and was told that the company now blocks all users from connecting to non-PCCW SMTP servers. This effectively blocks all home users from sending mail out through third-party servers using SMTP.
The tech support staff advised me not to use my personal e-mail server to send mail using my home account.
However, I could send my outgoing personal e-mail through the Netvigator server and I would have no problem. I tried and it worked.