This was obtained from the Support Portal knowledge base. Hopefully it helps.
What does the "Possible Delivery" feature do?
http://tinyurl.com/28zqcq
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What does the "Possible Delivery" feature do?
When the Possible Delivery feature is enabled, AsyncOS treats any
message as a "possible delivery" if it times out after the body of the message is delivered, but
before the recipient host acknowledges receipt of the message.
This functionality prevents recipients from
receiving multiple copies of a message if continuous errors at their
recipient host prevent acknowledgement of receipt. AsyncOS logs this
recipient as a possible delivery in the mail logs and counts the message
as completed.
The timeout is a TCP timeout; normally 4 minutes. SMTP will timeout before 4 minutes.
If this feature is disabled, the Email Security Appliance (ESA) will try to resend the message. If the feature is enabled, the message is seen as delivered.
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We have particular email host we seem to be having problems sending to. I am pretty sure its something o their end. But I am providing info from our Mail Flow Central logs. There is one that I don't believe I've seen before. Does anyone know what this means?
Date:
October 20, 2009 10:15:06 -0500
Last state:
Message successfully delivered to '@.com' at 'xx.xxx.xx.xx'. Response: ''possible delivery''
:?
