Yup.
Wrote a site using SwiftMailer, worked when tested locally. Client added it to their mweb hosting, emails wouldn't work. Spent a few hours trying to debug it, decided to try on my own private hosting, mailer works perfectly.
When I asked mweb if they were blocking ports the response I got was "The PHP code is wrong".
Useless provider, don't use them.
I've heard good things about Afrihost/Frikkadel, if you want local hosting. Otherwise consider DreamHost, you can get pretty good discount vouchers on hosting for DreamHost and they actually work...