email client / online client difference

I use thunderbird to connect to my ARMY AKO email account. I noticed the majority of the time, the client has difficulty completing sending email. (Though some gets through without timing out.) IF I go directly to the website and use their email I have no problems at all. What could be causing this? I'd rather use my client email program than to have to go the email site. Bear in mind this only happens sometimes, more frequently than I'd like, and I am also overseas.

not familiar with thunderbird, but have you checked the usual settings against those listed at your army email service?
-POP3/SMPT/etc settings and addresses
-secure login/passwords
-firewall(s), ports etc..

yes. The program does work, and the email works - just not all the time. Since we're using satellite here I think it is some firewall issue at levels above me. I was able to email out this morning. Tonight I was not.