It would help if you specified which version o Windows and IE/OE you are running.
In the meantime, have you:
a) updated your anti-virus (etc) software and run it recently? (You will probably have to pay for those updates, which shouldn't faze you - you pay for regular maintenance for your car, right? Same goes for your computer.)
b) updated your copy of Windows? (If it's Win95/98/ME, you have an orphan operating system, and should replace it as soon as possible.)
c) updated your copies of MS software? IE is at version 7-something, and OE at 6-something (I don't know for sure, I use neither of them.)
d) double-checked all settings in OE? It's especially important that you check the identities and passwords.
e) considered using another e-mail/newsreader program than OE? (Recommended).
Sometimes it works to delete the account from OE, restart and remove all remaining evidence of the account from OE, restart and set up the account again, and then, just for good measure, restart again.
Note that updating can take a long time, and may require several restarts. If you haven't updated recently, you may not even see all updates, since some of them won't work until prior ones are installed. So you should repeat the updating until MS's update site tells you there are no more updates available for your computer (or you don't need the available ones.)
If you are using wireless, it's possible that your computer is connecting to an external network, in which case that network may not let your machine send anything, and it may be filtering incoming mail, too. This just happened to us: the motel across the street has set up wireless access for its guests, and from time to time my wife's laptop latches onto that external network instead of our in-house one. Depends on where she's located. She could receive, but not send.