Receiving an Error message when trying to send an email

Question

Help
All of a sudden whenever I try to send an email I receive an Error message stating it cannot be delivered. The message suggests verifying addressee, checking SMTP server settings and verifying any advanced settings. I have tried different addressees, and all the information in the Mail Preferences looks accurate to me. Any ideas what could be causing this? It just started happening.
Any info is greatly appreciated
Susan
Quad Core   Mac OS X (10.4.6)  

Answer 1

Hi Susan,
Many ISPs have recently started blocking outgoing (smtp) mail via port 25 that doesn't use their own smtp server. (This is to try and combat spam).
There are generally two ways to overcome this:
1) Use the smtp server of the ISP that you are currently connected to. (If you have a laptop and connect from different places this may mean you have to select an appropriate smtp server at each location.)
2) Connect to your preferred smtp server on a port other than 25. This will depend on the setup of that server. For instance the Apple .Mac smtp server allows connections on port 587 (reference Apple support article: http://docs.info.apple.com/article.html?artnum=75124)
Graham