Symptoms

• MailEnable mail is sent and received with a significant delays or looks like it is not sending at all.

• SMTP Outbound queue is full.

• %plesk_dir%Mail Servers\\Mail Enable\\Logging\\POP-DebugXXXX.log shows errors:

  1/17/16 00:29:59        ME-E0125: Connection Refused: (203.0.113.2) was refused because the inbound connection limit has been reached.
  11/17/16 00:29:59       ME-E0125: Connection Refused: (203.0.113.2) was refused because the inbound connection limit has been reached.
  

Cause

Server is saturated with spam.

Resolution

1. Remove items from MailEnable white list at Plesk > Mail Server Settings > White list . Keep only 127.0.0.1/32

2. Increase maximum number of send threads in MailEnable console > SMTP > Properties > Outbound .

3. Increase maximum number of concurrent connections in MailEnable console > SMTP > Properties > Inbound > Advanced .

4. Rename SMTP queue folder or clear SMTP Incoming and Outgoing queues of spam messages. You may use the MailEnable KB-article .

Additional information

How to protect server from spam

Antispam Tools in Plesk