.dat file format

Question

My boss has been receiving attachments normally until recently when she got her m365 installed. When external parties send us emails with attachments, she will receive it as .dat format. However, we receive it fine and when we forward to her, she can receive it properly.

I read that it may be the sender issue but the senders have been sending attachments and this issue only happened to my boss. Any way to check whats wrong?

Answer 1

Hi @Echua ,

Something here might help:

How email message formats affect Internet email messages in Outlook
https://support.microsoft.com/en-us/help/290809/how-e-mail-message-formats-affect-internet-e-mail-messages-in-outlook

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(If the reply was helpful please don't forget to upvote or accept as answer, thank you)

Best regards,
Leon

Answer 2

Hi @Echua ,

My boss has been receiving attachments normally until recently when she got her m365 installed.

Are the boss and you using the same kind of email account(for example, both are Exchange account in the same organization)?
According to your description, the issue only happens after using Outlook 365 desktop client. So, in order to confirm if the issue is related to the Outlook desktop client, it is suggested to check these attachments directly from the web mail and see if the issue has any difference. Or, if possible, you could try to add the problematic email account to those normal Outlook clients and see if this issue could be reproduced.

Any update, please feel free to post back.

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