Btinternet rejected my password to obtain my E mails

This indicates either an incorrect password or server settings. Make sure your account is setup as follows:

IMAP
Incoming Mail Server: mail.btinternet.com
Port: 993 (this should be automatically populated if you tick the SSL Encryption)
SSL Encryption: Enabled (but not STARTTLS)
Username: your email address including the @btinternet or @btopenworld.com part
Password: your btinternet password
Root folder/path:
Folder separator: . (full stop)
Please do NOT enable "secure password authentication" (SPA). It's not needed when you use SSL encryption and won't work.
If your IMAP client supports it, we recommend you also set up the following folders:
Trash
Sent Items
Drafts
POP3
Server: mail.btinternet.com
Port: 995 (this should be automatically populated if you tick SSL Encryption)
SSL Encryption: Enabled (but not STARTTLS)
Username: your email address including the @btinternet or @btopenworld.com part
Password: your btinternet password
POP from folder: By default, POP will pull emails from your Inbox
SMTP
Outgoing Mail Server: mail.btinternet.com
Port: 465 (this may not be automatically populated on selection of SSL, so you'll need to check this)
SSL Encryption: Enabled (but not STARTTLS)
Authentication: PLAIN
Username: your email address including the @btinternet or @btopenworld.com part
Password: your btinternet password
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Hi
Being a BTinternet customer myself, I am not surprised that you have a problem IF what you have put here is correct because the server you require is "mail.btinternet.com" NOT "mail.btinternet.co" as you state.
Cheers

Contact BTInternet support to cancel the account and register for a new one

How to set up BT email on your iPad

Contact your mobile carrier for help

Make sure you enable SSL encryption.

SMTP

Outgoing Mail Server: mail.btinternet.com
Port: 465 (this may not be automatically populated on selection of SSL, so you'll need to check this)
SSL Encryption: Enabled (but not STARTTLS)
Authentication: PLAIN
Username: your email address including the @btinternet or @btopenworld.com part
Password: your btinternet password

Click the "password?" in "Forgotten password?" on the btinternet sign-in page.

Mail app doesn't require a password. Your ISP, from and to which Mail fetches and sends email messages, requires a password. Deal with them.

There was a problem logging onto your mail server. Your Password was rejected. Account: 'pop.mail.yahoo.com', Server: 'pop.mail.yahoo.com', Protocol: POP3, Server Response: '-ERR [SYS/PERM] pop not allowed for user.', Port: 995, Secure(SSL): Yes, Server Error: 0x800CCC90, Error Number: 0x800CCC92

make sure your password is correct because this error description states that your password is incorrect

here are the settings for btinternet, if you use "outlook" you must manually configure them!

• The POP3 server (incoming mail) is mail.btinternet.com
• The SMTP server (outgoing mail) is also mail.btinternet.com
• Both need your BT Yahoo! email address and password; you will have to tell your e-mail program that the SMTP server requires authentication.
• The SMTP server can use either port 25 or port 587.

The most common fault is to provide your ADSL username and password when your BT Yahoo! username and password is what's required.

good luck and regards