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Outlook 2016 - the name on the security certificate is invalid

Posted on 2016-08-23
Medium Priority
Last Modified: 2016-10-01

We have just installed a new windows 2012 server running 2 hyperv servers. One being our domain controller and the other being our exchange 2016 server.

We have this working OK apart from the SSL certificate integration. ie we were getting complaints on starting up outlook regarding an invalid or untrusted certificate. I presumed that once we obtained the correct SSL, this would just disappear.

Unfortunately, having just purchased our True ID SAN from geotrust, and installed it, we are still experiencing a warning on starting outlook. This is :-

The name on the security certificate is invalid or does not match the name of the site.

I have spoken with geotrust and they tell me its because it is looking for the internal exchange 2016 name, which  I can confirm is the case.

the name of the local server is exch2016.domain.local

Our SSL is to secure and

Geotrust say that we have to rename our local site to match??

Can anyone advise on what we need to do to resolve this problem?
Question by:nigelbeatson
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LVL 18

Accepted Solution

xtermie earned 1600 total points (awarded by participants)
ID: 41767003
It seems like the common name that you specified when you generated the certificate request for that Web site does not match the URL that is used to access the Web site. For example, if you access the site by typing an IP address or the server name, but the common name that is specified in the certificate request is, so that is why you receive the security message.

To avoid this warning, make sure that the common name that is specified when you generate the certificate request matches the URL that will be used to access the site.

If the URL that will be used to access the site cannot be changed to match the common name on the certificate, follow these steps:
1.Create another certificate request. Make sure that the common name matches the URL that is used to access the Web site.
2.Have your certification authority generate a new certificate.
3.Use the new certificate for the Web site.
LVL 18

Assisted Solution

xtermie earned 1600 total points (awarded by participants)
ID: 41767009
You can also check a related microsoft's article here:

Author Comment

ID: 41767055
many thanks for your reply.

I think my situation must be a little different, as when I asked about adding the local site to my San, geotrust told me that this was no longer allowed.

it is not actually a site which is causing the problem, it is outlook 2016 that is looking for exch2016.domain.local , and our Ssl only covers

I don't understand why the local copy of outlook 2016 does not trust its own local 2016 server, but as I can't add the local name to our Ssl, I presume that we have to somehow change the local name of the exchange server.

accessing exchange remotely works fine, so I am very frustrated that I am having this problem locally.

I will check out the additional link, to see if it helps.

many thanks
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LVL 20

Assisted Solution

by:Peter Hutchison
Peter Hutchison earned 400 total points (awarded by participants)
ID: 41767230
It is itrue that using .local in DNS for certificates is no longer allowed.

You need to configure exchange so that it will use public names d( where possible instead of .local ones. So for owa it will be, for autodisover it is, and so on.

Author Comment

ID: 41789141
sorry for the delay in updating this incident. I have been away on vacation, but now I'm back, will be addressing this issue.

will update you later today.

many thanks for your assistance

Author Comment

ID: 41789625
I have now run the digicert tool which changed our local settings to

I have ensured we have a Dns zone for
with an entry for autodiscover and remote (which we use externally) both pointing to the local IP address of our exchange server.

I can confirm that our current San covers both and but the warning when starting out look still appears.

I am very frustrated, so if anyone can provide any further assistance, I would be much obliged.

it would seem that outlook is still trying to reach exch2016.domain.local. is there anything to do on outlook 2016 to stop this?

many thanks
LVL 18

Assisted Solution

xtermie earned 1600 total points (awarded by participants)
ID: 41794053
One more thing to check as are likely to have these two registry settings:


With HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\AutoDiscover
for Outlook 2010

You must make this solution more robust by adding these registry entries:


The only lookup type that will be used now, is HTTP Redirect to the XML file. If this fails, there'll be no Autodiscover.
This is an excerpt from my documentation after having implemented this solution twice with different forests, not Office 365.

For more information see here:
Potential Autodiscover Issue During E-Mail Coexistence

Outlook 2007 unexpectedly connects to an on-premise Exchange Server 2007 server mailbox instead of an Exchange Online server mailbox
LVL 18

Expert Comment

ID: 41824607
good comments and recommendations provided by experts

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