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Is there a way to add a domain policy to a Windows 2008 domain that sets the attachments size limit for Outlook (various versions) and Windows Mail?

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up vote 2 down vote accepted

You're really better off doing this on your SMTP server, because it's not client-dependent.

The maximum message size in Outlook 2010 can be controlled with registry modification even for non-Exchange clients that are just using SMTP to deliver messages. Outlook 2007 and older versions do not have this functionality and rely totally on Exchange's size limiting functionality for their own limits.

I'm not aware of any attachment limiting size functionality in Windows Mail. Being that it's a home-user oriented product it really doesn't surprise me that there wouldn't be any such limit. Typically an ISP's mail server would provide the limiting functionality for home users.

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Thanks Evan. The remote SMTP already does this kind of check, but there's a problem because no one is stopping clients from sending 300+Mb attachments before they get rejected and with the poor internet connection of this customer it's a problem. Of course teling people not to send big attachments isn't of any help as they just keep doing it all the time. – Valerio Santinelli Nov 19 '12 at 16:21
@ValerioSantinelli - The only other reasonable solution would be to put an on-site SMTP server in place, configured to smart-host to the ISP. You could, at least, stop large attachments before they hit the Internet. – Evan Anderson Nov 19 '12 at 16:36

As best practice, you should be doing this on Exchange but i agree why waste time uploading (especially with limited bandwidth) to a hosted SMTP server when it will be rejected anyway.

Open the registry editor and browse to:

Outlook 2013:


Outlook 2010:


Then add a new DWORD value: MaximumAttachmentSize

Unlimited message size uses a value of 0. For a specific message size (recommended) enter the value in Kb.

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This is configured on your MS Exchange server, not via GPOs.

Setting Message Size Limits in Exchange 2010 and Exchange 2007. It has been already asked here.

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We haven't got an Exchange server, it's just a Windows Domain. Is it possible only with Exchange? – Valerio Santinelli Nov 15 '12 at 13:46
What mail server do you use then? This is a setting present on most mail serrvers. – Zoredache Nov 15 '12 at 16:57
That domain isn't using an in-house mail server. All of the clients talk directly to the remote SMTP server which is managed by an ISP. – Valerio Santinelli Nov 19 '12 at 16:20

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