Hawking SWR54G problems with email

A friend just bought a Hawking SWR54G router. Since connecting it between his DSL modem and computer he can no longer receive or send email from his SBC Yahoo client software. If he connects the computer directly to the modem everything works fine. When he connects his computer to the router via CAT5 the Internet works fine but he can not use his email program. Is there some obvious place to start troubleshooting this problem? He contacted Hawking and they said to do a firmware update but that did not solve the problem.

Hi, Firewall config problem? Try disabling it for testing. Tony

Per "friend" Hawking had him disable firewall settings in the router and that did not help. I don't know what settings these were. I doubt it's a Win firewall issue as he can connect directly to DSL modem and has no problem with his email program. I just called him to get clarification on his symptoms. He now says with Firefox he can receive email but not send. So that sounds like an authentication problem. But again, if he connects directly to modem there is no problem. He has "reset" the router a few times and started over. When "friend" signed up with SBC he installed all the Yahoo software crap on his computer so I don't know exactly what email client he is using. He is not too computer savvy and is having problems explaining his exact conditions to me. I was hoping that the fact that he has no problems when connected directly to modem and does have these email issues when the router is in line that this symptom would ring a bell with one of the experts that hang out here.

Hi, One thing he can test email by sending an email to himself. If it works, then? Also he could ping a know destination. Tony

Hi, I believe that's default setting unless he changed it. Tony