Fix: Outlook for Mac 2011 & Exchange 2007: Unable to send messages over ~5MB

After having scoured the Internet long and hard and trying a variety of solutions, I’m prepared to label this a “Fix” with the caveat that I’m not entirely sure which setting actually “did the trick.”  There are an abundance of forum posts out there about this very issue—I’d even gone so far as to place a (free) call into the Microsoft Outlook for Mac 2011 product support team, who in turn tried to convince me that the issue was with Exchange and not Outlook (which is not true, as this issue does not occur in Entourage 2008… a point I was unsuccessful at arguing).

Yes, I’m aware that Outlook for Mac 2011 (hereafter referred to as Outlook 2011, as there is no Outlook 2011 for PCs) communicates using the Exchange Web Services (EWS) instead of WebDav; however, Outlook 2010 (for the PC) also uses EWS without issue.

Anyway, onto the problem… when running Outlook 2011 and attempting to send a message over ~5MB in total, you’ll end up with the following error (check for the little yellow exclamation point on the bottom right of your screen):

…and when you click on the little yellow exclamation point, you get:


Outlook 2011 then drops the message that failed to send into your “Drafts” folder.

I narrowed it down to a total message size of ~5MB that failed in this way.  Note that I said message size, because even though your attachment size might be exact, the MIME conversion adds overhead to the messages (around 20-30% from what I’ve seen).

By way of example, this was the sending progress indicator for a message with an 8MB attachment (notice how it’s 9678 KB):


First, I updated the web.config files in the following directories on the Exchange 2007 server:

C:\Program Files\Microsoft\Exchange Server\ClientAccess\Sync
C:\Program Files\Microsoft\Exchange Server\ClientAccess\Exchweb\EWS

…in said web.config files, I modified the maxRequestLength attribute, changing it from the default of 10240 to 30720.

I then restarted IIS using the Internet Information Services (IIS) Manager snap-in, highlighting the server, and clicking Restart:


(Note that you may have to hit “Restart” a few times… the IIS Manager is a bit buggy and doesn’t wait long enough for IIS to stop before it complains.)

Unfortunately, I now had a new problem… when sending, I’d now get this error instead:


So I then updated the Send Connector (which in this case was going to a Smart Host (irrelevant… you can just update the default one)) to allow messages up to 30720 KB:


Still, no love from Exchange.  I found one other command on another newsgroup that I tried as a last-ditch effort.  I have duplicated & modified that command here.

First, I ran the command that gathered information about the value I was going to be setting, and popped up Notepad, which I could then use to search for the requestFiltering section and verify that the maxAllowedContentLength attribute (set in the next command) was not yet present:

%WINDIR%\System32\appcmd list config "Default Web Site/owa" > currentConfig.txt & notepad currentConfig.txt

Once I confirmed that maxAllowedContentLength was not present in the requestFiltering section, I ran the following command to add it and re-check the current configuration:

%WINDIR%\System32\Inetsrv\appcmd.exe set config "Default Web Site/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:31457280 & %WINDIR%\System32\Inetsrv\appcmd.exe list config "Default Web Site/owa" > currentConfig.txt & notepad currentConfig.txt

If you’re wondering where I came up with 31457280, that’s 30 MB in bytes, that’s right, bytes.  If you set this value thinking it’s in KB, you’re going to break your ability to send anything but the smallest messages.

Here we can see the value set up:

At this point, I restarted IIS again (per my aforementioned procedure) and attempted to send my slew of test messages… they all went through, as we can see in the Sent Items in Outlook 2011:


…and in the Inbox of my OWA account:


Needless to say, the client was very pleased to now be able to send e-mails over 5MB in size.

If you’re wondering why I didn’t test beyond 10 MB, it’s because many recipient e-mail systems won’t process messages that large—and as such, I don’t recommend to clients that they send anything over 10 MB as a “general rule.”



18 responses
Thanks for the walkthrough. It came in handy.

Just thought I'd note that SBS (2008 or 2011) users will be using the following scripts instead:

%WINDIR%\System32\appcmd list config "SBS Web Applications/owa" > currentConfig.txt & notepad currentConfig.txt

%WINDIR%\System32\Inetsrv\appcmd.exe set config "SBS Web Applications/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:31457280 & %WINDIR%\System32\appcmd list config "SBS Web Applications/owa" > currentConfig.txt & notepad currentConfig.txt

Thank you very much for this article. one thing is on the second command you are missing the inetsrv dir.... other than that you fixed me good!

Thank you again!

@Mike... thank you! I've updated the command :-)
I have been looking for such for sometime now.
I am on SBS2008 and tried your commands and got the following error

ERROR ( message:Unknown attribute "requestLimits.maxAllowedContentLenght"

Any clue?

Many thanks


You do realize there are three different commands up above

1st - Checks the current environment.

%WINDIR%\System32\appcmd list config "SBS Web Applications/owa" > currentConfig.txt & notepad currentConfig.txt

2nd - Changes the value

%WINDIR%\System32\Inetsrv\appcmd.exe set config "SBS Web Applications/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:31457280 &

3rd just verifies the changes.

I put all three commands into a notepad and ensured spacing was right. i was able to get all three to run.

I ran the command on exchange 07 on sbsb 08 in the command window not exchange shell..

hope this helps!

Mike Perry

Thank You Mike
I cannot understand why this is happening, i am typing it correctly, anyway I decided to copy/paste the whole command from your blog and it worked. Absolutely funny.

By the way on Garretts command line the Inetsrv path is missing. Should be

%WINDIR%\System32\Inetsrv\appcmd list config "SBS Web Applications/owa" > currentConfig.txt & notepad currentConfig.txt


%WINDIR%\System32\Inetsrv\appcmd.exe set config "SBS Web Applications/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:31457280 & %WINDIR%\System32\Inetsrv\appcmd list config "SBS Web Applications/owa" > currentConfig.txt & notepad currentConfig.txt

Thank you

Hey good to hear.

I did point out that on my first post and he fixed it above but not in the comments...

Very glad it worked but i still have it showing its ugly head from time to time..

I am running very new G5 with OS X Lion.

I am running SBS 2008 with 07 exchange fully patched.

The users on the macs started to notice they could not send emails over 5mb. They would act like they sent or would give a resource not available error, the email would also be dropped into a secondary "drafts" folder. I have applied all updates to the mac and have submitted several trouble tickets with no resolution.

My workaround was to use web-mail via the exchange until apple and MS get the known! issue fixed.

I do know outlook 2011 for mac uses different services than the PC version of outlook uses.

need any help just drop me an email..

Thanks to this post for bring us together

-=UPDATED=- command up in article is not correct....

Delete this Brian once you fix it.

%WINDIR%\System32\Inetsrv\appcmd.exe list config "Default Web Site/owa" > currentConfig.txt & notepad currentConfig.txt

%WINDIR%\System32\Inetsrv\appcmd.exe set config "Default Web Site/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:31457280

%WINDIR%\System32\Inetsrv\appcmd.exe list config "Default Web Site/owa" > currentConfig.txt & notepad currentConfig.txt

I do have this issue.
will this work for exchange 2010 sp1 environment

I still have never totally resolved this. My mac users use the outlook web access to send any larger sized emails.<o:p></o:p>

From: Posterous [mailto:

Hey this post was the only one that I found that mentions addressing maxallowedcontentlength that it must be in BYTES. Made the change and it's working! Thanks!
Thanks for this great post.
Any idea how to do it on Windows 2003, IIS 6 and Exchange 2007 ?
My users have this issue and my environment is Exchange 2007 with IIS 6 on W2k3.

The appcmd.exe seems to be missing. Any idea, how to resolve this issue?

On exchange 2007 you have to manually set the send and receive connectors. both are set very low. This problem is only related to MAC using a different method to send email on outlook 2010. what are your clients? OS and office version?<o:p></o:p>

From: Posterous [mailto:

Thanks for your reply and sorry for my delayed reply.
My users are on Snow Leopard (10.6) using Office 2011.  If I attach and send the same file via OWA, it goes through.


It should be located above…<o:p></o:p>

Do you have all components of IIS installed on the server under add and remove programs ???<o:p></o:p>

From: Posterous [mailto:

It is not there.  I am using server 2003 btw.  I read somewhere that it's only part of 2008.
The IIS has Common Files, IIS Manager and WWW Service installed.  Do I need any other components?

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