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A few of my users were getting rejected by a remote server when trying to send/receive attachment of 9-10Mb.

I tried the following command 

Set-TransportConfig –MaxSendSize 10MB –MaxReceiveSize 15MB

This did not work.

I ran the following command 

Set-TransportConfig -ExternalDsnMaxMessageAttachSize 100 MB -InternalDsnMaxMessageAttachSize 100MB -MaxReceiveSize 100MB -MaxSendSize 100MB

This allowed the users to send and receive attachment size in the 10MB size.

My question is why do I have to increase the attachment to 10 times more than what I intended to do for it to work?

Thanks

Ruben

Diamond
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Rubmay
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1 Answers1

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Base64 coding grows the size of attached file by arround 1.3. So if you want to send a 10MB file, the email will be arround 13MB plus the headers and the body part. So, you need 15MB minimum. You should define –MaxSendSize 15MB to solve your problem.

Dom
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  • The reason you have to set the send and receive size the same, is because when you send an email through Exchange it is both sent (by the sever sending the email) and received (by the server receiving the email) even for internal traffic. If the users are on the same server, then it is still "sent" and "received" due to the hub transport architecture in Exchange. – Sembee Feb 02 '16 at 11:33