Whichever port your email account is set to use for SMTP (sending email), the network at work has it blocked for outgoing traffic. Why? You'd have to ask your email or network administrator.
Sometimes, if you add your work email address as an account in your phone, and use that to send emails, it works. That way you're using the work email server to send the emails and it can check for viruses, etc. That's one reason they may be blocking outgoing emails to another server. (Of course there are other "reasons". In one case that I know of, and helped someone overcome, the "email administrator", really an administrative assistant who knew nothing about computers, read something about viruses getting into open ports, so he blocked a lot of outgoing ports.)
