Whenever you send or receive an email message, it may have to pass through many different mail servers throughout the Internet in order to arrive at its final destination.
Sometimes these servers may take a varying amount of time to process your message, and sometimes the network links between servers may be down, or running slowly.
Another common reason for a message being delayed, is that one of the mail servers is using a Spam detection technique which deliberately delays a message in order to filter out genuine messages from spam and other junk mail. This spam filtering can sometimes delay a message for an hour or more.
The email system does not provide guarantees on when a message gets delivered, and sometimes you may experience a delay between the time the message is sent and the time that it is received.
As an email service provider, we can only provide you with the ability to send and receive messages, but we can not offer any guarantees about delivery time as these sort of delays are well outside of our control.