NTLWorld.com just stopped working. Says IMAP not connecting to server.

It would be helpful to see what error code is returned by the SMTP server in this situation. From a desktop or laptop device open a Command Prompt in Window (or otherwise a Terminal) and enter the following where username:password is replaced with your email address and password, i.e. richard.branson@virginmedia.com:rotavator-racecar-tenet-repaper:

curl -v smtps://smtp.virginmedia.com -u username:password

Do not post the resulting output here but instead review it for possible reported causes, i.e. VM error code; choosing to ignore this advice and posting the unredacted or incorrectly redacted output here will likely reveal your email address, password and / or public IP Address.

FYI if there is no issue then you should see the following output from the curl command:

⋮
> AUTH PLAIN
< 334 
> [Redacted]
< 235 2.7.0 SMTP350 Authentication successful for user [Redacted]
> HELP
< 214-2.0.0 This is cmsmtp ESMTP service help
214-2.0.0 This is cmsmtp ESMTP service help
< 214-2.0.0 To contact postmaster send email to postmaster@virginmedia.com.
214-2.0.0 To contact postmaster send email to postmaster@virginmedia.com.
< 214-2.0.0 For local information send email to Postmaster at your site.
214-2.0.0 For local information send email to Postmaster at your site.
< 214 2.0.0 end of HELP info
214 2.0.0 end of HELP info
* Connection #0 to host smtp.virginmedia.com left intact

Otherwise an unsuccessful result will look similar to the following:

⋮
> AUTH PLAIN
< 334 
> [Redacted]
< 525 5.7.13 Authentication Denied (VM320)
* Closing connection 0
* TLSv1.2 (OUT), TLS alert, close notify (256):
curl: (67) Login denied

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If the resulting curl output mentions netreport then go to https://netreport.virginmedia.com/netreport/ and:

• select an abuse type of Email Sending Errors from drop down list
• select an abuse form of Other from drop down list
• paste the complete error message into the Log Evidence area
• enter your name into My name field
• enter your email address into Email address field
• select Submit button

Hopefully de-listing will occur sooner rather than later but if not post back here to have the issue flagged to the forum team.

Also, if appropriate,. consider following the advice here My Virgin media email has been hacked | Virgin Media Help