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This is not a problem with MailMarshal SMTP. Usually, this issue occurs because of a poorly configured intermediate router not sending the proper message back when the maximum packet size (MTU) is exceeded. The key clue here is that as soon as MailMarshal attempts to send the DATA portion of the message (typically a larger packet size), the message times out.
ping -f -l 1472 202.37.162.129
Pinging server [202.37.162.129] with 1472 bytes of data: Reply from 202.37.162.129: bytes=1472 time<10ms TTL=128
ping -f -l 1473 202.37.162.129
Pinging server [202.37.162.129] with 1473 bytes of data: Packet needs to be fragmented but DF set.
"Packet needs to be fragmented but DF set"
If you establish that this is indeed a problem with an intermediate router, your investigations should focus on that device. You may need to contact your service provider (ISP) for help if it appears there is a problem outside of your own jurisdiction. As stated above, this typically is not a MailMarshal problem, and as such it is very possible that we will not have a MailMarshal-based solution.
This article was previously published as: NETIQKB29349 Marshal KB185
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