Same here with my 'ntlworld.com' email address. My email client reported the account wasn't available at around 23:00 on Sunday 18th June. Still not available twelve hours later.
The Server Status number is acknowledging email issues but not providing any ETA for a fix. Server Status page is just showing "Sorry, we can’t run a test on your services right now".
Looking at my email client logs it appears to be an issue only for my primary account, other secondary accounts do appear to be able to login in , some redactions -
* Account 'XXX': Connecting to POP3 server: pop3.virginmedia.com:995...
[2023-06-19 12:26:13] POP< +OK Virgin Media server ready.
[2023-06-19 12:26:13] POP> USER XXX@ntlworld.com
[2023-06-19 12:26:13] POP< +OK
[2023-06-19 12:26:13] POP> PASS ********
[2023-06-19 12:26:14] POP< -ERR [AUTH] Authentication failed.
*** error occurred on authentication
*** Authentication failed.
* Account 'YYY': Connecting to POP3 server: pop3.virginmedia.com:995...
[2023-06-19 12:26:19] POP< +OK Virgin Media server ready.
[2023-06-19 12:26:19] POP> USER YYY@ntlworld.com
[2023-06-19 12:26:19] POP< +OK
[2023-06-19 12:26:19] POP> PASS ********
[2023-06-19 12:26:19] POP< +OK Logged in.
ADDED : Actually not quite, for a different secondary account -
* Account 'ZZZ': Connecting to POP3 server: pop3.virginmedia.com:995...
[2023-06-19 12:42:12] POP< +OK Virgin Media server ready.
[2023-06-19 12:42:12] POP> USER ZZZ@ntlworld.com
[2023-06-19 12:42:12] POP< +OK
[2023-06-19 12:42:12] POP> PASS ********
[2023-06-19 12:42:15] POP< -ERR [SYS/TEMP] Account is temporarily unavailable.
*** error occurred on authentication
*** Authentication failed..