I'm just checking out MobileMe since now you can add your own email address on the web app which looks promising. I've always hated Gmail but it does work for custom domains and it's free. I also just setup my iPad to check MobileMe and am able to send with my custom email address through Gmail's SMTP server but I can not get this to work on OS X Mail. When I change the email address for my MobileMe account in Mail, it fails to send via MobileMe's SMTP server. If I try connecting to gmail.smtp.com it also fails. Does this not work with OS X Mail?