For the company I work for (hotmail|live|msn) addresses come third, making up about 1 in 5 users. That’s actually more than I would have expected, and I suspect is largely due to the audience not being very technically savvy.<p>GMail just pips Yahoo to the top, both making up about 1 in 3 users each.<p>Hotmail seems to just magically disappear e-mails at random; they never end up arriving with our customers. Yahoo frequently “defer” delivery until later which can be very annoying when sending out verification e-mails. We’ve never had any problems with GMail delivery at all.<p>Following the advice on the pages below has helped resolve some of these issues, but if I were a user of these services I’d rather receive the odd spam e-mail or it end up in the junk folder instead of having to wonder if e-mails were occasionally going missing.<p><a href="http://postmaster.msn.com/" rel="nofollow">http://postmaster.msn.com/</a><p><a href="http://help.yahoo.com/l/us/yahoo/mail/postmaster/basics/postmaster-15.html" rel="nofollow">http://help.yahoo.com/l/us/yahoo/mail/postmaster/basics/post...</a>