Some SMTP-mail not received

Normally all SMTP-mails are received by Domino SMTP-server from pop3 mailcollect-application(Mailtraq), and delivered to the notes users.Log shows:

SMTP Server: Message 00275791 (MessageID: xx@yy.com) received

SMTP Server: 127.0.0.1 disconnected. 2 message[s] received

But only sometimes(seems to be randomly in time and recipient) the SMTP-connection is established, but the Domino SMTP-server is not receiving the smtp-mail (Address is OK), and it is returned to the sender.

Log shows:

SMTP Server: 127.0.0.1 disconnected. 0 message[s] received

Any suggestions of solving the problem, or Tuning the Domino SMTP-server ?

Subject: Some SMTP-mail not received

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