Hi! I have encountered this issue on iPhone 5 (7.0.2), iPhone 5s (7.0.1) and iPad Mini (7.0). The problem is that I have 2 SMTP servers assigned to one of my mail accounts. When I am sending an email using the cellular data, the iPhone simply cannot connect to the primary SMTP server (which is ok, I understand why) so that I have another (secondary) SMTP server provided by my carrier which works well.. Now the problem is that when I am sending an email using the cellular data iPhone simply won't activate the secondary SMTP after unsuccessful attempt to connect to the primary one and won't send the emal. In order to send the email correctly, I have to turn manually turn off the primary server and then the device use the secondary one and everything works well.. Is that a bug in iOS 7? Does somebody have the the same problem?