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Issues
451 Remote connection lost - psmtpSymptoms
What does it mean when Postini's servers return the "451 Remote connection lost - psmtp"?
Resolution
The sender server sees the error, "451 Remote connection lost - psmtp".
The error indicates that the Postini server has lost its connection to the receiving mail server when it was expecting an acknowledgment of the SMTP DATA command or message completion. This is a symptom of some sort of networking issue between Postini & the receiving mail server during an SMTP session, or an issue on the receiving server.
The issue can occur with both inbound and outbound mail flow. If it is occurring with inbound mail flow, "receiving server" refers to the Postini customer's mail server; i.e. the server listed in Delivery Manager. If it is occurring with outbound mail flow, "receiving server" refers to the server to which Postini's outbound service connected when trying to transfer the message.
If this error message occurs only with calendar invite messages, the issue may lie with your firewall configuration. Both Sonicwall and Watchguard firewalls have functionality that can be set to deny the MIME type that denotes a calendar entry. To receive these calendar messages, this needs to be removed from your mailserver.
This error normally occurs on an intermittent and limited basis, but could be consistent with certain types of messages, such as messages over a certain size. If it is occurring with a widespread number of sending/receiving domain, do not hesitate to contact Postini Customer Care in case it is a symptom of networking issue with Postini's network providers.451 Remote connection lost - psmtp
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