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Outlook 2016 - "Failed to resolve recipients. Operation failed. This is usually caused by a bug in GpgOL"
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I have a problem with Outlook 2016 and gpg4win.

If i want to write a new email, click on the "sign and encrypt" button and then "check names" i get a error.

Message is "Failed to resolve recipients. This is usually caused by a bug in GpgOL".

Here are 2 screenshots. Sadly my Outlook is in german language. I hope this is still ok.



Outlook 2016 & gpg4win-3.1.3

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aheinecke triaged this task as High priority.
aheinecke added a subscriber: aheinecke.

Thanks for the report.

This has the same underlying problem as T4129 which was only reported in German. I'm not closing this report here as it is in English and thus better find able.

I've already committed a fix for this with rO3c0a66e402e8

I'll upload a patched gpgol.dll with that fix soon.

aheinecke changed the task status from Open to Testing.Sep 7 2018, 10:59 AM

If you like you can help by confirming that it also works for you by installing 2.3.1-beta11-STABLE-BRANCH-2-3 from as described under:


First let me say; Thank you very much for your help ! :-)

Sadly the new dll still doesn't solve the issue. Was there any (major?) change between Release gpg4win 3.1.2 and 3.1.3 as in the older version it's running fine.
Might this be maybe related that we use Office 365 as cloud solution ? I send you debug logs which maybe help in default level "1" as also detailed level "1922".

Best regards,

Yes we had a bug in 3.1.2 that when you had a contact group as recipients gpgol would silently ignore them and don't encrypt to them.

We fixed the contact group support in 3.1.2 and additionally added the message you are seeing as a safeguard against such failures in the future. But that safeguard is overly zealous as apperantly in some circumstances, like the one descirbed here the recipient resolution runs into errors. But that is ok temporarily and should only be messaged if the error persists when the actual encryption happens.


I made a mistake and put the DLL in the wrong folder. After placing it into the correct one, everything is working fine and stable.

Thank You very much and greetings from Germany !