Sorry if this screws things right up, but unless anyone knows better, I do think you'll find yourself running into this! I have some ideas for working around this (eg. a central server taking direct messages from the clients and then sending out the emails to registered users), but they'd be outside my abilities to implement...
Cheers for the info. We haven't encountered that on any PC we've tried it on yet.
I don't think it screws things up. We can add the pop 3 stuff as a backup option. Its not the end of the world if some people can't get it working. Email play is only one aspect of the game.