Why Size of a Message gets increased when status changes from Draft to Sent?

Question

Hello Support Team,

I have observed that when I creates a message contains body and subject along with to/cc mentioned and save it as a draft then the size of the message is less e.g. 2.91 kb as compare to the message size when it sent (e.g. size became 6.9kb).

My questions here is what are the possible reason which is causing size of the message increased when status change from Draft to Sent?
Could you please elaborate and explain technically because I am using graph API to restore message using POST call of /messages and during testing I observed it, which is size discrepancy between Draft and Sent Message. Are there any headers or any metadata which is getting embedded whenever message sent, if yes then what are those headers/metadata?

Thanks

Answer 1

Hi Dharmendra,

 

The size of the message can change because of content conversion, encoding, and transport agent processing.

 

Content conversion:

Content conversion is the process of correctly formatting a message for each recipient. The decision to perform content conversion on a message depends on the destination and format of the message. For example, convert plain text format to HTML format. The latter tends to be larger than the former because it contains more elements and formatting information.

If you want to know more about Content conversion, see https://learn.microsoft.com/en-us/exchange/mail-flow/content-conversion/content-conversion?view=exchserver-2019.

 

Encoding:

                The main excoding that affects the size of the message is the based64 excoding, which increases the size by about 33%.

 

Transport agent processing:

                Once the mail is sent, it goes into the transport pipeline, and is processed by many transport agents. These transport agents have anti-spam, content filtering, address rewriting, RMS excryption and decryption functions and so on. Pipeline tracing creates an exact snapshot of a message before and after it encounters each transport agent. If you’re curious about how the message changes with each transport agent, you can try it out.

                About how to use Pipeline tracing, see https://learn.microsoft.com/en-us/exchange/configure-pipeline-tracing-exchange-2013-help

 

As for headers and metadata, yes, some of them will be embedded. For example, when a message is routed to a sorter component on the transport service, the destination of the message is marked as the NextHopSolutionKey attribute on the recipient. And the DKIM record inserts an encrypted digital signature into the header of the message using the private key, then the recipient uses the signature to determine whether the received message is legitimate. However, they generally do not increase the mail size significantly.

 

I hope that’s a useful answer.

 

Best wishes,

Kelly