Emails with attachments teams channel

Frequent Contributor

Hi everyone,


We have an issue where when people send emails to a channel with attachments larger than 10 MB the email will not arrive and no reject will be sent.

We tried to set up a transport rule to reject the message according to Microsoft teams channel limits article, but it doesn't work.

Here is the link: Emailing a channel 

And here is my transport rule:



We also tested several messages with various attachment sizes and this also didn't tell us why the email isn't arriving to the channel.


As far as message trace from exchange the email is delivered. I don't know where else to check because we don't limit anything there.



4 Replies
best response confirmed by RahamimL (Frequent Contributor)
Emails sent to channel aliases are routed through a "shadow" tenant, so their processing is a bit of a black box for us as customers. Message trace, mail flow rules, NDRs - they only affect a part of the process, and we have zero control over the rest. Just live with it :)
Sorry for the delayed response.

If I understand you correctly, I need to open a ticket with Microsoft to check the matter further?

Doesn't hurt to try.
So the official answer from Microsoft is to create a transport rule rejecting the email because the total size of the message is GE 10 megabytes...
Go figure...