Exchange Online Message Sizes

What’s the deal here? When you start dealing with attachment sizes with Exchange Online and especially in a hybrid environment you start to realize how complex the subject can get, and just how little control you have…I mean you do have some control, but Microsoft likes to steer you and limit what control you actually have…I find this a tad unfortunate, but also helped me quickly get my answer when I struggled.

First of all, I ran into an odd situation. All of the literature I had read has told me that Exchange online had huge limits on their email, but whenever I tried to send an email externally or to someone on-premise, I got a bounce back saying

The message is odd…so checking the usual suspects. On-premise, I would typically go to check Transport Config settings.

hmmm odd, why would these be unlimited? If you do a little bit of research you’ll notice that the set-transportConfig commands are only available on-premise online. You cannot set these in Exchange Online…

as an side note, I find it frustrating that Microsoft limits you in this manner…

Moving on, if I can’t set size limits using set-transportconfig, the size limits must be on the mailbox/mailbox policy itself.

ok, this lines up with what I know from Microsoft. It looks like my attachment sizes are actually 150 MB…and if I want to change then, I can do it here for individual mailboxes or for a plan. However, this still doesn’t help me solve why I can’t send more than 10 MB, moving on. Sometimes you have to read the error message over and over again to actually clue in to where the issue is occurring…

Remote server of course…I didn’t check the send and receive connectors in Exchange 2010. In Exchange 2010, the Send Connector is found under Hub Transport > Send Connectors and the Receive Connector is found under Server Configuration > Hub Transport. Both were set to 10240 KB (10 MB).

I changed both to a more agreeable number, just make sure it lines up with what you’ve already established in Exchange. You wouldn’t typically see this message If you were routing your mail out of Exchange Online, however, we are currently routing out of our on premise environment until we migrate that piece over.




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