Hello,
The client's Mail server IP is not blacklisted in any major RBLs. Also, there is no recent spamming from their IP.
But messagelabs.com blocks the IP without providing any error messages.
From client server,
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# nc -v cluster5.us.messagelabs.com 25
nc: connect to cluster5.us.messagelabs.com port 25 (tcp) failed: Connection timed out
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From another server, we are able to connect without any issues.
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# nc -v cluster5.us.messagelabs.com 25
Connection to cluster5.us.messagelabs.com 25 port [tcp/smtp] succeeded!
220 server-15.tower-119.messagelabs.com ESMTP
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Please advise , how we can solve the issue.
Thanks in advance.