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I just installed Outlook v15.9 as well as updates for the entire new Mac 2016 suite released yesterday. I'm getting an Outlook certificate error as can be seen in the attached screen shot. I can click Continue and run Outlook without any problems and it works fine. Also, I wasn't getting this error in the immediate prior release. All of my company's email is hosted on Office 365. How can I fix this or should I worry about it? Thx! John
Using older versions of Outlook for Mac in business environments
Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.
I'm the OP on this I think :-)
I can confirm as well that same error occurs on 15.13.1. For me however, this error has never gone away since first seen in 15.9.
I have this same certificate error now.
I can confirm that I did not have this error until I installed Microsoft Outlook update 15.13.1
My other thought is they are trying to put SNI support in their clients.
I bet a fix for people would be to create an SNI certificate and put it on their web server along with whatever other domains they have there (assuming the web servers support SNI).
Hi! I was in contact with Microsoft support about the issue, the response was:
Outlook 2015 is outside our support boundaries , but we have some insights in the issue:
Following are the details I have on the certificate prompt:
. The prompt for the certificate warning is from the MAC OS because we are using the OS's network stack (due to the network improvements in 15.9), so the prompt is expected.
. If you choose to "always trust" it once it shouldn't prompt you again, or the certificate issue can be fixed to prevent this from occurring.
. As a test, you can enter the AutoDiscover URL into Safari and you should also see the Certificate warning prompt.
So it looks like they are aware of the issue, they did not however, respond to my question if it's going to be fixed until full release...
(Outlook 2015, I assume they mean 2016)
//Christian
I ran into this and dug a bit deeper with Wireshark. When Outlook starts, it does a DNS lookup of your domain (I guess in your email address). This will be an A record pointing to yourdomain.com. It then tries to connect to 443 to one of the IP's returned from the lookup. If it succeeds, it uses that certificate to build the chain. If the certificate returned is different than yourdomain.com then you'll get the certificate warning.
I don't know if this is new behavior, but I didn't see this until I upgraded to 15.10, and I guess others saw it at 15.9. Not sure if it's a bug or a new feature.