Email Woes

I have been having email problems for a couple of months now. I had no idea until just recently. My incoming emails come through fine (at least I think that I am receiving everyone's messages) but outgoing messages go nowhere apparently when I use my laptop. If I email someone from my Blackberry it goes through though. Weird, huh? I don't get how that is happening. I use the same email address either way. If anyone knows how to possibly fix this, please let me know. I hate not having my regular email!