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.”