I have a number of machines (win2k & XP) running Office 2000 and Office 2003 that upon sending emails using SMTP only tranmit at 40KB/sec max whilst others transmit at full rate. (100Mb switched network).
I dont think its the emial server as most of the PC's can SMTP to it a full speed. On the PC's that are slow to TX to the email server i mapped a network drive and copied a 20MB file which only took a couple of seconds as you would expect. POPing from the email server on the same machines are fine too. It seems only SMTP outbound traffic is affected. On my Laptop which is one of the slow ones im running XP Pro, Office 2003 i tested sending a 20MB email to the server in both Outlook and Outlook Express and both of them exhibited slow SMTP transmissions.
Looking at the email server as it receives the SMTP packets its almost as if the client is throttling them as the throughput stays almost exactly at 40KB/s. I took my laptop home and put it on my home LAN and again it was slow to send SMTP mail.
My thinking so far is that it something on the client. Ive disabled the anti virus software, Thought it may have been activesync but one of the PC's in the office that is slow does not run Activesync.
Any ideas would be greatfully received !