It's possible that you are configured correctly but the network you are on is blocking outbound port 25 smtp. If you are currently on wifi, turn it off and try your 4G and vice-versa. Some networks block port 25 outbound for spam purposes. ie they block the sending of email.

The email server at PSA is antiquated. Modern servers use Active Sync which works everywhere as is simple to setup. Having said that, their webmail works very nicely on a mobile device and you may like that better.