Mail delivery freezes. Mail cannot be delivered. How to troubleshoot?
Make sure that:
SMTP service as well as other Mail services are running.
SMTP port 25 should not be blocked by firewall.
IP address of DNS server is set correctly in "Mailenable Management>Servers>Localhost>Connectors>SMTP>Properties->dns servers".
Mail queue is not full.
If you use Mailenable, make sure that mail queues are not full:
C:\\Program Files\\Parallels\\Plesk\\Mail Servers\\Mail Enable\\Queues\\SMTP\\Outgoing
C:\\Program Files\\Parallels\\Plesk\\Mail Servers\\Mail Enable\\Queues\\SMTP\\Inbound
Apply Mailenable solutions to deleting mails if it is nessesary:
5.Check mail logs in C:\Program Files\Parallels\Plesk\Mail Servers\Mail Enable\Logging\SMTP
6.Check spam folder, mail can be recognized as spam.