Calendar integration with Microsoft Outlook fails to send messages

[rafamartinc]

Hi,

I reported this issue to customer support back in October but, after several months, they are clearly unable to find a solution. I hope it goes better here...

Expected Behavior

Around a year ago, I could send calendar invites from Microsoft Outlook (desktop version for Windows 10) without issues, through the Bridge app. I could just create a meeting in Outlook's calendar, choose my ProtonMail account as sender, and that was it. It worked seamlessly.

Current Behavior

Since 4 months ago or so, whenever I send a calendar invite from my ProtonMail account, using the desktop version of Microsoft Outlook and ProtonMail's Bridge application, a new mail appears in the Inbox folder with the title "Undeliverable: [original_subject_here]". The calendar invite never arrives to the recipients. It happens the same if I try to edit or delete the invite in any way, and for every meeting where the Bridge app is involved. Sending a calendar invite from the web portal works perfectly, and also works in Microsoft Outlook for every other mail provider I work with. The issue only happens with Outlook + ProtonMail bridge.

Possible Solution

As this worked a few versions ago, something must have changed in the Bridge app that made it partially incompatible with Microsoft Outlook. The customer service offered a few possible fixes, such as upgrading to the latest version of the Bridge app (I am in v3.0.10 now), reinstalling it entirely, setting up my ProtonMail account in Outlook again, etc. None of them worked.

Steps to Reproduce

1. Create a new meeting in Microsoft Outlook's desktop version.
2. Select your ProtonMail account as sender.
3. Hit "Send". It will fail, never arriving to any of the recipients, and a warning message will appear in ProtonMail's inbox.

Version Information

Currently v3.0.10, but also every one that has been available since Sep2023.

Please let me know if any logs or tests are needed. Thanks,

[gabor-meszaros]

Hi @rafamartinc, Thank you for reporting this issue and I am sorry that you have this problem. We have just received your latest logs via customer support, and have already started to investigate it (GODT-1804). I will leave this issue open, but because all the previous conversations are on the customer support portal, please continue the communication there. Thank you!

[LBeernaertProton]

A fix for this issue has been release with v3.0.16.

[rafamartinc]

Hi. I have v3.1.1 and I am still receiving the same error. Could you please share if any additional steps are required, apart from updating the Bridge? Thank you!

[LBeernaertProton]

@rafamartinc can you send regular messages to those recipients?

[rafamartinc]

Yes, I can. That works without issues.

[rafamartinc]

Still not working. The issue was notified in January, and to customer support back in October 2022...

[LBeernaertProton]

@rafamartinc Do you have any text in the message or calendar invite that are part of a non latin alphabet (e.g: Cyrillic) ?

[LBeernaertProton]

Also, is this a local calendar or one managed by Microsoft?