Winmail.dat attachment

NethServer Version: 7.9.2009
Module: NethMail

I use a mac with Mail to manage mail connected to the NethMail server. From some senders who send me an email with an attachment, I happen to receive a Winmail.dat attachment instead of the correct attachment.
I noticed it only happens on MACs.
Is there any way to fix it?


Hello @Nicola_Lorusso

And welcome to the NethServer community!

Winmail.dat is an old, at least 25 year old problem and still exists.

It is NOT a problem with any Mac or any Mailserver, but actually the problem of the sender. These often seem to be older Outlook (Office) versions.
You can read up on the Winmail.dat problem (eg search Google), it’s been around for at least 25 years now! And it’s always Outlook (Usually older version) doing wrong encapsulation for an attachment. Once entered into Outlooks profile / Addressbook, even if you use Outlook on a different PC (under Windows!) you’ll still get a Winmail.dat file…

My 2 cents

1 Like

No, does not happens only on Mac OS or iOS

The sender should configure better Outlook/Exchange. Several software are available to “unpack” the message/attachment contained into the Winmail.dat file. I never look for any for Mac OS but… I’d try a run into the web for some more info.

You might want to take a look at tnef. Convert the winmail.dat from the cli.


The best way is to try to update outlook? I don’t know how to set better settings on Outlook.

And this is not a Microsoft-product support community.


Very simple!

Ask the user of Outlook to buy a newer Version…

That’s how you upgrade MS Products, they’re commercial, after all.
→ If it’s someone outside your organization, it’s anyway out of your control…

My 2 cents

IIRC the Outlook user needs to disable RTF.


IIRC the Outlook user needs to disable RTF.

if I remember correctly it is a configuration that has to be done at the exchange server level (if the client has one).

1 Like

I think this setting can be done on client (Outlook) and server (Exchange) side.


We have NethMail as server mail and each user has ms outlook (or mail if Mac).
I can’t set this on Server side (it’s not exchange)

OK, so you need to use HTML or plain text in Outlook. RTF creates the winmail.dat issue.

1 Like

It’s a configuration that has to be done at the sender’s outlook or exchange level, on your end you can’t do much…