Can only send and receive email through WiFi.

[Yvonne13]

I am only able to send and receive email when near a WiFi source. Out in the open away from WiFi I receive a message "The Mail Server mail.btinternet.com is nor responding. Verify you have the correct info in Mail settings" or "Cannot connect to the Outgoing Mail server for myname@btinternet.com". I then have the option to try a repair which results in "Connection to the outgoing server mail.btinternet.com failed".
I have checked the settings against those on my computer, all seem to be identical, and had a long chat to BT who say all is set up correctly and that I should contact EE. Phone lines are busy and queues are long so I never get through.
When I return home and venture near the WiFi area I am immediately flooded with all the email messages built up during the time I've been out.

I'm using an iPhone 9 Plus and running iOS 13.6 but email has never worked correctly so it seems technology is letting me down in this instance.  Any ideas??

[XRaySpeX]

@Yvonne13 : What have you put as the Incoming & Outgoing Server settings in your Mail app, obscuring your name?

Is your PC connected to the BT BB network? If so, that is why it works there. Your phone isn't & might need diff settings.

[Yvonne13]

Thanks for replying to this damsel in distress. This isn't a new problem; I've had trouble for about 2 years but it's never really bothered me as I' haven't been that desperate to read my email, until now.

Have just been on EE chat line and got in such a mess that I ended it. The operative kept on about Gmail passwords and I kept repeating that I don't have a Gmail account. He sent a profile download and this has changed all my settings from those that I had and those that I have on my Mac. Also I was starting to be told it was all BT's fault and I hate it when the buck is passed!

Anyway, the incoming server seems to be my email address and the outgoing server is mail.btinternet.com.
I'm using a Mac and yes connected to BT BB.

[XRaySpeX]

All the settings please,, not just the servers' names, just obscuring your names.

[Yvonne13]

Is this what you need? These are the settings since EE messed about yesterday.

IMAP ACCOUNT INFO    
Name                   my email address
Email                    my email address
Description         my email address

INCOMING MAIL SERVER      
Host Name          mail.btinternet.com
Username            my email address
Password             *******************

OUTGOING MAIL SERVER
SMTP                   mail.btinternet.com

[XRaySpeX]

Nowt about Ports, SSL, TLS? Default values of these won't work off-BT BB network. 

[Yvonne13]

Sorry, not quite sure what info you need but Server Port is 993, SSL is on and I can't find any reference to TLS.

[XRaySpeX]

OK, that's some settings for the IMAP Server. Now tell me that for the other 2 servers. Every setting is significant even if unticked, unset or None.