Server Not responding Message while using Internet location document

I have a remote user who consistently receives “Server Not responding” while using the his Internet Location Document in the Notes Client.

He states: Next problem is about 50% of the time when I make an email and hit send it just loops and after about a minute I get a message that can not connect to server (or something like that). Hit send again and it goes out immediately. I am on internet setting which I like since I can work on emails and use lotus notes while I receive and send messages. He is generally sending 4 - 6 megs files.

I have verified that our Domino Server is up and running, I have no one else reporting this issue. Any suggestions to the cause? Any help would greatly be appreciated. We run iSeries platform, Domino version 6.5.5 FP2 and the notes client is 6.5.5