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Windows 7: Outlook 2007 slow throughput for attachments

23 Jan 2013   #1

windows 8.1 Pro x64
Outlook 2007 slow throughput for attachments

Ok so is no confusion the issue isnt a slow connection to the mail server or slow to submit email it is a low throughput. Since normal emails are tiny they go fast but if I eg. send a 1meg file over smtp email it is slower than eg. ftp.

My connection is 20mbit upload so approx 2.4mbytes upload so no confusion.

So my web server which I manage is my primary email server, it also has ftp as a transfer protocol. As well as a webmail interface.

If I upload the file to the ftp it uses all my upstream bandwidth.
If I send an email with the file as an attachment using webmail it uploads and is sent in under a second.
If I send the email via smtp using outlook it sends at around 200kB/sec.

The following all have no affect on the speed other than stated.

Disabling a/v
Changing the smtp port.
Disabling tls/ssl.
Enabling ctcp increases the speed to 250kB/sec, which is still hideous barely over 10% of my possible speed.

I havent tried another email client such as outlook express or thunderbird, or outlook 2010.

I suspect the issue is that outlook is hardcoded to a small tcp send buffer as a typical end user doesnt have a fast upload connection when outlook 2007 was developed. If so is there a way to tune it higher (or is it really hardcoded non tunable) or is there other ideas to speed it up.

My System SpecsSystem Spec
27 Jan 2013   #2

Windows 7 Home Premium 64 Bit

Have you checked outlook for any possible addins? Your anti virus may have added a plugin.

As a test, open outlook in safe mode, (not windows safe mode )
Send a test and track its speed.

Your outgoing smtp is your broadband providers right ?
My System SpecsSystem Spec
28 Jan 2013   #3

windows 8.1 Pro x64

the anti virus does have an addin but its been disabled for testing.

the smtp server is my own smtp server I personally manage not my broadband isp.

Since I still havent got this resolved, I will try thunderbird as well as a newer outlook to see if they have the same issue. As I still believe its due to a hardcoded low send buffer value.
My System SpecsSystem Spec


 Outlook 2007 slow throughput for attachments

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