Notes dog slow replicating mail to hosting comp, MTU problem HELP!

Internet speed it great. Only when I replicate with my hosting company’s mail is it dog slow. I was told it is an MTU problem Adjusted two registry MTU settings to 1500 plus wireless router and laptop are set to 1500. I’m not an admin, I’m a developer and don’t know the inner workings of MTU settings. Can anybody help?