Originally Posted by Solarmoon
The most annoying one is usually the block or redirection of port 25 (outgoing email from your machine when you don't use webmail). They often set up a non-encrypted SMTP relay that they want you to use instead. The reason given for this is ostensibly to block SPAMMERs from using their internet service to connect to thousands of open relays out there.
The biggest problem I have is that some hotels use services that have SMTP servers, but the hotel staff doesn't know the SMTP server name or address. So sometimes my SMTP server software will work (PostCast Server) but sometimes it won't.