Issues sending encrypted email from one user to another

As a test of your email certs (before using them in the real world), I signed up for 2 certs with the same name but different email addresses, let use these as an example:

jdoe[at]company.com
jode[at]personal.com

I am using Outlook 2007 on XP for jdoe[at]company.com and Outlook 2007 on Windows 7 for jdoe[at]personal.com.
I went through the process for configuring the certs in 2007’s trust center and each account sent a signed message to the other. Each account then added the sender as a contact, and I can verify that a certificate is listed under the contact’s properties. I checked and for some reason in Outlook the user jdoe[at]company.com on XP was set to 3DES encryption. Jdoe[at]personal.com on Win7 has many more encryption options, and was set to AES 256-bit. I changed this to match 3DES setting on the other user (who has no AES options).
Now, when I send an encrypted message from jdoe[at]company.com to jdoe[at]personal.com, it works as expected. But, when a jdoe[at]personal.com sends to jdoe[at]company.com, I get the message:

Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities:
jdoe[at]company.com
Hash algorithm is the same for both: SHA1, both are set to use S/MIME

What is happening? I am not sure how to resolve.

C’mon anyone? I can’t proceed until I solve this issue …

Have you tried changing it back to AES 256?

Changing things to AES doesnt do anything.

Basically, I set both to 3DES. (XP account was that by default, changed Windows 7 to that from AES256). Windows 7 user can send to XP user successfully (XP user can view encrypted email). XP user cant send to Windows 7 user.
Both certs were from Comodo, using defaults. Checking further, the only difference in the certs is:

Windows 7 user’s cert shows:

Signature algorithm: sha1RSA
Signature hash algorithm: sha1

XP user’s cert shows:

Signature algorithm: sha1RSA

  • there is no entry at all for signature hash algorithm in this certificate.

Any help? Is it possible to open a ticket for this matter??

Hi stty0,

Please submit the ticket in the following link
https://support.comodo.com/index.php?_m=tickets&_a=submit

One of our representative will respond to your query.