I think your asking two questions:

First, you may need to consider a service like SpamArest. It sits between your email POP provider and you, looking for possible Spam. You give it a list of addresses that are acceptable to start with. If you get an email from someone other than on the list, Spamarest sends them an email that requires a response for confirmation. This is thought to help reduce spam sent via automated systems. This should help get down the total amount of message, which should then speed things up.

As far as an alternative for getting email whiel on the road. There are quite a few. I heard about this one recently that people seem to think is good.