Can't send emails from mobile/tablets following password change - solution

[HarryW]

I've recently changed passwords on both mine and my wife's email accounts following the Yahoo issues.   I updated all of our mobile devices as well and then discovered that none of them would send emails.   On the Android, I just deleted the account and reinstalled and everything worked OK.  I tried doing this with our iPAD and iPhone but still the problem persisted.  This particular issue is on the btinternet domain (Yahoo used to be the email supplier), so I am not sure whether it's the same everywhere, but I found a little gem on the help pages of BT:

"Be aware, before I fixed this problem I deleted the account and set it up anew.  It verified and I thought it was all OK.  But it wasn't - the old outgoing password was retained even though the account verified, meaning that outgoing messages failed.
 
It turns out that when you change your password on an iPad it only changes the INCOMING mail password.
 
To change the outgoing mail password you have to go into Settings; then scroll down to Mail, Contacts, Calendars. 
From there select the BTinternet account and select the account where it is listed under IMAP.  
 
You will find the details for the account and can change the password for the Incoming Mail Server there, but the outgoing mail server simply shows SMTP and mail.btinternet.com
 
If you tap on the outgoing mail server it still shows very little detail and that it is 'on'.  But you have to tap on that Primary Server in order to find where the Outgoing password is hidden so you can update it.  I only noticed the difference because my new password was longer than the old one and when I found this page realised it was wrong."

I've followed this method and it does work.   As a matter of interest, I tried just updating the passwords but this doesn't seem to work, you need to delete and reinstate the account first.