I was having a similar issue. At home, using wireless, any emails I sent would sit in my outbox regardless of anything I did. I would then take my laptop into my office, plug into the LAN and and any emails in my outbox would be sent.
This evening while at home again, I went into manage my account >more settings >advanced and changed the Outgoing SMTP from 25 to 587. That now allows me to send emails from my home wireless.