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# SMTP: ERROR Write and ERROR Read Messages

Article ID: 112237

Article Last Modified on 10/30/2006

APPLIES TO

- Microsoft Mail Gateway to SMTP 3.0

This article was previously published under Q112237

## SYMPTOMS

The Mail Gateway to SMTP displays "ERROR write" and "ERROR read" messages.

## CAUSE

There is a problem in the TCP/IP layer of the network transport. If no other errors indicate an obvious cause, the most common one is mismatched TCP/IP window sizes.

## RESOLUTION

Define the window sizes in the gateway computer's TCP/IP layer and the TCP/IP host to be in the same range. The best method is to make them the same size and the minimum size allowed. If window sizes match but network errors persist, use a protocol analyzer on the network segment between the gateway computer and the TCP/IP host to pinpoint their cause.
REFERENCE KB on "TCP/IP Sliding Windows Concept"

Additional query words: 3.00 smtp tcpip windows

Keywords: KB112237