Incoming Emails .msg attachments missing/not coming

Recently I worked on one issue which was very interesting, in fact easy to troubleshoot but difficult to believe/conclude the results.

One of our users raised an incident ticket with my team and it came to me for research and debugs the issue. The issue based on ‘incoming email settings’. More than 10-20 users send an email with attachments to SharePoint document library in which incoming email functionality is enabled.

What exactly the issue is?

If I send an email with an .msg file as attachment then the attachment goes missing. If I send an email by attaching word document, excel document or PDF document then it works properly i.e. email goes to the document library as per the expected behavior.

Note: One think I would like to highlight is “.msg is not a blocked file type” in any blocked extensions which are provided by MS list.

Troubleshooting done:

-block file types already checked in central administration: no difference

-if the settings in the incoming email document library are set as per unique permissions then we can change it to “any sender” settings for the troubleshooting purpose

-tried changing the settings “save all attachments in folders” to “save all attachments in the root folder: didn’t make any difference

-tried changing the mime type by means of outlook (to be specific: from MIME to UUEncode or BinHex): didn’t make any difference

Note: this issue is not machine/user specific. This is complete farm issue in which you can cross verify on any portal/web application.

Conclusion: this seems to be a by design behavior/Product limitation of the SharePoint.

If anybody has a perfect resolution for this then please shares the same here so that it would be very helpful for all the SharePoint communities. Thank you