Outlook 2019 The Name on the security certificate is invalid or does not match

Outlook 2019 on premises connecting to Exchange Server 2016 on premises... We kept getting Certificate Security Alerts when Outlook would open and periodically when using Outlook. The issue was Outlook was connecting to my Exchange Server by the internal servername.mycompany.local and not the autodiscover.mycompany.com or mail.mycompany.com. This was driving me and my users crazy. I looked for days for a solution... reviewed and verified my local and my domain DNS settings, set my virtual directories to be the same using ECP, looked at Active Directory Sites and Services and the SCP Lookup. After countless hours trying to either fix this issue or at least suppress the pop up, I finally found a great resource on the web which I will link below. When reviewing the output txt file, I saw the results of the "Get-OutlookAnywhere | Format-List" to see the issue. The ExternalHostName and InternalHostName did not match. Used the Set-OutlookAnywhere command to fix it:
Web Site Reference:
www.ajtek.ca/g...
Command that fixed it (you will have to edit for your server/sites):
Set-OutlookAnywhere -Identity: "exchangeservername\Rpc (Default Web Site)" -InternalHostname autodiscover.mycompany.com -InternalClientsRequireSsl $true

[@pedroescalona2004]

I went through this search and I pass in front of it several times until I watch your video. Definitive was the solution. A few weeks later I run into the Exchange 2016- Server and double click and guess what? in The GUI the last option was the Outlook Anywhere configuration😯😑

[@ajcopeland3044]

this got me on the right track, I needed this and to make the autodiscoverurl null since we are in a hybrid config. thanks

[@TheIndica321]

Just completed the journey. I now have internal and external urls all pointing at the Fqdn for my organisation Internally that fqdn has a dns entry pointing at the-internal ip for mailbox/cas server Public dns points at our public ip and i port forward 443 to our internal ip for the mailbox/cas server Hint-: Left control and right click on outlook system tray icon and select connection status to identify the published urls your outlook is connecting to and checking ssl certs for. Read the whole url! Mine was /mapi prefixed with the internal domain name, so i then knew to change the relevant service in aj’s Transcript output Works like a charm now thanks for the video Message if you wish. What a mess ms made

[@sumeshkumarsoman860]

Tnx for the info.but in my case idid auto discover option for fetching internal exchange outlook access on azure ad joined PC's and start fetching email's as well.But the problem is, still this pop is coming.

[@jp_r00512]

I owe you a beer for this. Thanks!

[@stevenvnwyk3]

This worked for me.. Exact same situation I missed it because the default command I found didn't list Internal and External Url. Thanks so much

[@philfyphil]

I have been at this for over a week now, when I saw this I felt really hopeful on fixing it. However, for me it made absolutrely no difference. Unbelievable. I am clost uninstalling the entire server and using something else!

[@TheIndica321]

same as that. great video, exactly my condition but still presenting internal domain! to externals

[@seanroberts3585]

DUUUUUDE! i was on this for like 3days YOU ARE A CHAMP, THANK YOU let me go have a beer. DONE XD

[@Devmasterv]

good info. do we need to restart the IIS server after the change?

[@michaelwest7649]

I tried your suggestion and completed AJ Tek's other recommendations (minus the backup procedure). Still getting error. I scrolled down to the bottom of page to "OK, I Got All of That. What About Troubleshooting?" and I added the 8 Registry tweaks and my certificate issues resolved!! I've been chasing this for over a year. I can check off the box now.

[@Thekenzki]

what are the 8 registry tweaks you added

[@mjsigns1]

Is it safe to assume that you run the commands from Powershell?

[@nkanyisonkaman815]

If my outlook 2016 is connecting to exchange server 2010, can I try this solution?

[@sumeshkumarsoman860]

If you can,Please help me by recommending and option for the below issue to.

[@rickdorsey9000]

Something from this video or the guide by AJ Tek fixed this for me but it did not start to work until I deleted my outlook mail profile in control panel and created a new one to start over. Hope this helps someone.

[@okram8282]

Thank you so much