Score:0

[Send mail with attachment]: TCP Retransmission, Duplicate ACK => TCP Reset

tj flag

So, we have a linux box with postfix running on LAN site A which sends emails to an Microsoft exchange server sitting on site B. This runs perfectly when there is no attachment to the mail. But as soon as there is an attachment with a size of around 2 MB and up, the mail will not be delivered. Instead the client retranmits the same packet 8 times before it will reset the TCP connection picture from the client

vidarlo avatar
ar flag
What's path mtu? Is the connection via some VPN that has lower MTU?
A.B avatar
cl flag
A.B
Supposing there's information to retrieve from the capture, it's incomplete: the capture is one-way. The return traffic could have been of interest but is not included (and could also give a hint for vidarlo's question too). Also, if the capture could be text rather than screenshot it would even be better.
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