: Outlook 2016 says "The target principal name is incorrect" on my site's security certificate I currently run a Plesk VPS, with 2 Domains hosted within. Some time ago, I had installed the 'Let's

@Fox8124981

I have managed to resolve the issue.

Step One:

When you first see the 'Internet Security Warning', select 'View Certificate'.



Step Two:

What you then need to do, is identify who the Certificate has been issued to. Refer to the below image, for where to find this information. Once you have identified the location, copy the entry exactly as is.



Step Three:

Head into your Outlook and then head into File > Account Settings > Account Settings. You should then be on a page, which looks something like:



Simply select one of your emails by double clicking on the relevant account.

Step Four:

Referring to Step Two, simply paste in the 'Issued to' information into the Incoming mail server and Outgoing mail server(SMTP) text boxes, as highlighted in the below image.



Step Five:

All that is left to do now, is to click 'Next' and continue as you would normally. Then repeat the process for the other emails.

Where I was going wrong, was that I had mail.domain.com entered into the Incoming and Outgoing server text boxes. This was ok for a while, since I hadn't installed an SSL Certificate onto my server but now that I have an SSL Certificate, I needed to change my entries, to reflect the name of my server, which the SSL Certificate was installed on.

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