Software :: Not Fetching Emails Over Wifi

The last time I used Mail to manage my emails was in mid last year. Now, after a long time I plan to use it again but I seem to be running into problems. But before that let me give an idea of my setup: I have MacBook running Mac OS X 10.5.6, I have setup wifi over my isp's broadband connection. My router is Airlink101 Super G Wireless Router AR430W. I have MobileMe subscription. I setup Mail with my MobileMe and Gmail IDs over my wifi, both as IMAP accounts. Gmail is sluggish but received all my emails but MobileMe doesn't receive my emails at all. I want to assure you that I have set it up properly. I reported this problem to MobileMe chat support, they concluded that there was some problem with my network. They suggested me to port forward the following ports 25, 587, 143, 443 and 993. I tried that but still Mail was unable to fetch emails. I could send and receive emails via Safari i.e. web interface. I had setup security in my wifi, I disabled every thing by reseting the router and used the non-secure default setup. Still Mail doesn't fetch emails. I removed the wifi set up and connected to internet directly via ethernet. Now Mail works perfectly and fetches my emails at blazing speeds. Now the question is why doesn't Mail work in wifi setup. I need wifi setup by all means. I'd like to know what could be the problem?