Pop3

[AJ310865]

Why wont my Pop3 emails send over EE mobile data but ok on wi-fi?

[bristolian]

POP3 refers to receiving emails, I presume you mean SMTP which is the outgoing equivalent.

Most providers require you to be connected using their service in order to use their outgoing SMTP server - who is your email provider?

Do they have an option to use authenticated SMTP?

[XRaySpeX]

What port are you using for your SMTP Server?