Try setting the account up manually using the settings here https://www.bt.com/help/email/manage-email-account/manual-settings/what-are-the-settings-for-outgoin...
Thanks but have also tried that without success.
Dan
@DanMeehan Are you using a VPN on your mobile?
If it's only affecting your mobile and you're not having any issues accessing your email on any other email clients or via the website it does point to a problem with the phone.
Thanks
Neil
Sorry but this was a problem on my previous mobile. Having just purchased a new phone I wanted to get the issue sorted - but obviously no solution. Thanks anyway.
A couple of things to try.
Go to your MyBT and check under manage email that your account type is shown as 'Standard'
If it is, stop any devices trying to access the email account, change your email password in webmail, wait at least an hour to give the servers chance to sync password change and then try setting up the account again on your mobile.