Are there problems with Microsoft's POP3 Connector?

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Microsoft’s implementation of the POP3 protocol appears to make erronous assumptions about the way the internet manages TCP/IP packets.

TCP/IP is the transport mechanism that is used to send packets of various lengths of data around the Internet. The TCP/IP protocol may divide any packet into smaller ones as it routes the information from the source to the destination. For example, the packets may be routed over a low speed link which can only manage 48 byte packets. In this case, TCP/IP will divide a larger 10K packet into lots of pieces and send them over the low speed link. TCP/IP guarantees that all packets will arrive at the destination in the right order but DOES NOT guarantee that the packets will be recombined to be the original length.

In Microsoft’s implementation of the POP3 connector, they ASSUME that the terminating CRLF.CFLF appears in one, single packet. This means that anyone using the POP3 connector over a link may experience problems collecting email.

GMS usually deliver the CRLF.CRLF as two packets (i.e. CRLF and then .CRLF). Due to Microsoft’s failure to comply with TCP/IP standards, this can cause problems when mail is collected from GMS.


Gordano Ltd will be altering the POP3 protocol driver to cope with the problems introduced by Microsoft.

A work around for this solution is to change the bandwidth parameter for the delivery of email through POP3 to about 5K but this also slows down the delivery of email.

Keywords:microsoft pop3 connector

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