Can't send emails help please!

I have an IMac G5 running 10.5.8. I was having a problem with some emails not deleting. I would click delete and they would gray out but would not go to trash, if I would go to another address and come back, they would be in the black again! I did some research and the "Rebuild" was suggested, so I tried it and WHALA the emails were finally gone. Now I can receive emails without a problem, but I can't send any! I have 4 email accounts and all of them will not send out anything! I have a gmail account, 3 road runner accounts and an account from my website and none of them will send out anything! I have checked my settings and nothing has changed, the only thing that I have done is the rebuild! I hope I have given you enough information!

Hopefully someone can help!