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Wednesday, December 06, 2006

What is the largest file attachment that you can send via Exchange and a few related incidents for the ACA Guy

Summary: Setting attachment size limit is the right thing. But, what is the biggest file that you can send via Exchange theoretically? And, see how ACA Guy sent a 6.5GB folder.


There is no denying that Microsoft Exchange is a highly successful product. With more than 115 million seats (users) worldwide, this email solution has become an integral part of many organizations and it is difficult to fathom how business processes get completed without it today!

(And, in the interests of equal time, the same applies to Lotus Notes and GroupWise users.)

All the same, even a "killer app" like Exchange has its limitations, such as sending large file attachments. Exchange and its related desktop client products, Outlook and Outlook Web Access (OWA) all have limits on the size of files that can be sent and received.

In a prior discussion on MSFT Exchange/Outlook attachment size best practices, it was noted that, out of the box, the Exchange 2003 sets the default file size at 10MB. Email administrators can adjust these limits higher or lower. Setting higher file size limits allows end users to send or receive large files, but these higher limits can result in performance degradation of the overall system. And, from talking with email administrators, setting file size limits in the range of 5MB to 10MB seems sufficient for the majority of email users and business processes. Moreover, it helps to control email performance issues which impact the entire organization.

(So, why is ACA Guy so up to snuff on Exchange/Outlook? Many Accellion customers come for SFTA's ability to integrate with Exchange/Outlook so that large file transfer capability becomes a seamless process for their Outlook users. But, that is, as the saying goes, another story for another time.)

Looking at the size limit issue from the other side, for the sake of argument, what is the biggest file that an user can send under the Exchange/Outlook regime? For this, let's turn to the official MSFT Exchange team blog.

In the posting about Controlling attachment size in Exchange Server 2007 Outlook Web Access (OWA), Raj Mukherjee noted there is a default file size limit of 30 MB. Raj also provided instructions for email administrators who want to change that file size limit, and the instructions are, shall we say, non-trivial.

On the question of the hard limit, Raj discussed OWA's 60 minutes time out for file uploads and downloads which cannot be changed even by an email administrator.

So, it kind of got me thinking. Since one hour is a decent chunk of time, if you take the trouble to send a very large file, I cannot think of a worse fate than having the job abruptly terminated mid-session when the clock strikes the 61st minute.

Oh, beyond self-loathing from the terminated job, did I mention how you would also get the evil eyes from all the people whose email comes to a crawl because you attached large file in the email?



Never one to shirk from controversies, ACA Guy was drawn into a war of words in the comment section for the Exchange blog posting. It is a shame that "Mr/Ms Anonymous" left the party. Nevertheless, here is a Digg entry if you want to keep the flame alive.

Finally, for the record, ACA Guy's biggest file transfer job was a 6.5GB folder with one click through an Accellion SFTA box.

Just thought you would like to know.


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