Mail.app: S/Mime encrypted attachments are not working under MacOS Sierra

The problem still persists: MacOS 10.12.3

The workaround, dragging the mail to a folder and open the .eml, works for me, but this is not the way it's supposed to work, isn't it? Making the exchange of encrypted mails more difficult will not lead to a widespread use of encryption I guess. Apple seemed to be interested in being a company concerned about privacy...?

Yes I can confirm, that it works under 10.12.4 but just for mails received under 10.12.4. Older attachments in mails

still need the workaround. Even rebuild of the mailbox doesn't help. Presumably, one has to empty some caches instead but I didn't try that.

cheers

RF

Interestingly, if I send an encrypted attachment to myself, I can open it in Mail. If anyone else sends me an encrypted email containing an attachment, I have to drag the message to the desktop, double-click on it and open the decrypted attachment from there.

Hi all:

nwikner is right. Same problem for me , I just tried it out from my accounts. However, it works for all my mail accounts, even at different providers, but all sent via Apple mail, Version 10.3 (3273), from the same machine to each other respectively.

Getting a mail from a third party even through one of my providers doesn't work. Very strange ! still som work for apple.

br

Ralf_F

I have the same problem see my post on attachments import.

Mail attachments disappeared with Sierra

have the similar issue, see

Re: cannot read attachment of encrypted mails

that's really bad.

running your own mailserver behind a firewall, let you forward yourself the mail unencrypted to read/store the attachment, and throw away the unencrypted staff thereafter.

However, this can just be a workaround for <1week.

apple it's ridiculous.

Have the same bug here: since upgrading to Sierra I can not open the encrypted S/MIME attachments in Mail.app. They are still visible but not to open. All other attachments in the other email accounts (without S/MIME attachments) are working.

One workaround is to search in the mails download folder for the attachment you want to open:

-> ... /Library/Containers/com.apple.mail/Data/Library/Mail Downloads/

In my case some I could open, some not.

Come on Apple: S/MIME encryption is a real business feature. Really bad, to have to say our clients "sorry, but since the last OS update from Apple we are not able to open your confidential attachments."

Hope there's an quick solution or better workaround out there.

I'm seeing the same issue. Sierra Mail is reporting there is an attachment but but the attachments are coming through as 0k in size. Looking in the sent messages folder, even the original does not show the proper attachment. Have had to turn off encryption entirely using Mail. Very frustrating.

+1 here. Same issue. Attachments either don't come through at all or disappear from the message when I try to move it to another folder.

Another user pointed out the possibility of the new space optimization function having something to do with it. Any thoughts there?

I don't have storage optimization enabled and attachments come through (and stay viewable) if the message is not encrypted. I think it's just a bug in the Mail.app.

I disabled the optimization too. Yes it's a bug in the mail app.

I accidentally figured out one workaround. It is to drop the mail out of the app to the desktop and open it there.

It can be opened and the attachment will open too, i.e. decryption works.

Strange but true. The desktop copy can be deleted afterwards.

best regards

Ralf_F

Yes, I can confirm that dragging the message with a ? attachment in Mail to the desktop then double-clicking the x.eml file to open it in Mail does decrypt the message with attachment. I believe this means that all of the messages are still fine and not corrupted, it is just a bug in the Mail app and, when fixed, archived encrypted messages with attachments will display properly.

The workaround Ralf_F mentioned works for me, too. Thanks a lot for that. Now we can read the encrypted attachments again, until Apple will fix this bug. Based on experience this will take some time 😉

Had the same issue and I found a potential solution that seems to solve the whole SMIME issue with the mail.app for me at least.

Go to keychain and find your certificate. Open the private key, go to the 'Access Control' tab, check if the mail app is there, close it (I didn't have to change anything), restart mail and you should be done. It seems as if you need to tickle the cert a bit to get it back activated. Bit strange but it works.

Cheers.

//W