COMODO Email Certificate - Microsoft Office 365 (Plan P1) - Outlook 2010


I have an Office 365 P1 subscription.

I’ve brought in my own domain (

I’ve set up Outlook 2010 on my PC to access my Office 365 email

I’ve installed an email certificate from COMODO for

If I try to send an email signed using the COMODO certificate for the 365 account I get an error message: “Microsoft Outlook cannot sign or encrypt this message because you have no certificate which can be used to send from your e-mail address.”

If I use the registry setting SupressNameChecks then signed 365 email is sent ok, but I have several email (POP3/Exchange) accounts, each with their own certificate and want to have Outlook select the correct certificate depending on which account is being used.

The certificates are installed and Outllook 2010 configured correctly. Everything works fine apart from the Office 365 account.

Any ideas?



August 9th 2013 and still no joy.

I’ve compared my settings with a friend with a similar set-up. The only differences are I’m using Windows 8 Pro and he has Windows 7 Pro and his Office 365 domain ends .org and mine ends .net.

  • Our ISP is the same.
  • Our equivalent DNS settings are the same with the ISP and our Office 365 accounts.
  • We both use Outlook 2010.
  • We both have multiple email accounts on different domains and providers each with its own COMODO certificate. The only issue is with my Office 365 hosted email. His is fine. All other accounts work fine for both of us.
  • He can send email using his COMODO certificate and Office 365 account, I cannot.

COMODO will not respond on this issue; it is a free certificate so I’m not surprised, but I am disappointed.

Microsoft will not respond with any sensible suggestions. Very disappointing.

Any ideas anyone?

There are many ways to get free support, for your free COMODO products.

I recommend you go to this link, and use the SUPPORT LIVE CHAT (at the right upper corner).

Best Regards,

I’ve tried the various support routes. I even had a ticket/case number at one point. They made a few standard, but not relevant suggestions, then they went silent and haven’t responded to any contact attempts since.

What about the live chat?

Have you tried also GeekBuddy? Is free as far as I know the very first days.

What have Microsoft said?
After all it is their software, Comodo are only providing the certificate.

Have you raised a support request with Microsoft regarding how their software functions?
If yes, I would suggest posting their response here.
If no, I would suggest doing so, as well as asking for assistance here.


Yes, silence from both :frowning:

One silly question, as I know it happens.

Is the email address on the certificate exactly the same as the one you are sending from?

As per this knowledge base article:,128,96,32

Also worth checking the other knowledge base articles in that section:,128,96