Problems deleting SMTP server

Hi there - I'm having problems sending emails through my personal email server. I've tried changing the SMTP account passwords but it doesn't log me in. So I created a new account on my server and tried to change the SMTP credentials on my phone but it kept reverting to the old one. I deleted the email account on the phone and then re-entered it but somehow the old SMTP information keeps being used when trying to send out emails. I can receive emails fine... Can anyone help?