Check if port 110 is opened.
Also check that these are like this:
SMTP_BLOCK = "1"
SMTP_ALLOWLOCAL = "1"
I know this is smtp, but often smtp authentication first is used to pick up pop3 mail.
Some also set smtp_block to 0... but oke.. I wouldn't.
Normally it should work when port 110 and 995 are opened in the firewall.
Also check this setting:
PORTS_pop3d = "110,995"