Sometimes, Outlook users experience error such as "Outlook conflicting or unsupported encryption capabilities"  which occurs when the email address of the contact or recipient is different from the email address that is specified in the recipient’s certificate.

Here at Ibmi Media, as part of our Server Management Services, we regularly help our Customers to solve Outlook related issues.

In here, you will learn how to fix this Outlook error.

More information about "Outlook conflicting or unsupported encryption capabilities"?

Basically, when we send an encrypted email message to a recipient, Outlook uses the recipient's certificate to secure the message.

In a case where the email address differ from the email address that is specified in the recipient's certificate, you will receive the following warning:

Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities:

Continue will encrypt and send the message but the listed recipients may not be able to read it.

To prevent Outlook from displaying this warning message, we turn off e-mail address matching for certificates.
When we send a secure message in some Outlook versions, we may need to use a certificate that does not match the e-mail address.
In this guide, you will see how our Support Experts turned off e-mail matching for certificates.

What factors triggers "Outlook conflicting or unsupported encryption capabilities"?

The most common cause is that we tried to send encrypted messages without having a copy of a valid certificate for the recipient.
If we have multiple contacts for the recipient, we must send a message using the contact that has the certificate.

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How to fix "Outlook conflicting or unsupported encryption capabilities"?

The fact is that in order to fix "Outlook conflicting or unsupported encryption capabilities", you need to turn off the multiple contacts.
We can turn off e-mail address matching for certificates by editing the registry.
To do this, you should follow the following steps, as per the version of Outlook you are running:

For Outlook 2013, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK.
ii. Locate the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\15.0\Outlook\Security:
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\15.0\Outlook.
b. On the Edit menu, point to New, and then select Key.
c. Type Security, and then press Enter.
iii. Then, do a Right click the Security key, select New, and then select DWORD Value.
iv. Type SupressNameChecks, and then press Enter
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

For Outlook 2010, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK
ii. Locate the following registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\14.0\Outlook\Security
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\14.0\Outlook
b. On the Edit menu, point to New, and then select Key
c. Type Security, and then press ENTER
iii. Then do a Right-click the Security key, select New, and then select DWORD Value
iv. Type SupressNameChecks, and then press Enter
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

For Outlook 2007, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK
ii. Locate the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\12.0\Outlook\Security
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\12.0\Outlook
b. On the Edit menu, point to New, and then select Key
c. Type Security, and then press Enter
iii. Right-click the Security key, select New, and then select DWORD Value
iv. Type SupressNameChecks, and then press Enter
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

For Outlook 2003, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK
ii. Locate the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\11.0\Outlook\Security
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\11.0\Outlook
b. On the Edit menu, point to New, and then select Key
c. Type Security, and then press ENTER
iii. Right-click the Security key, select New, and then select DWORD Value
iv. Type SupressNameChecks, and then press Enter
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

For Outlook 2002, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK.
ii. Locate the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\10.0\Outlook\Security
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\10.0\Outlook
b. On the Edit menu, point to New, and then select Key
c. Type Security, and then press Enter
iii. Then, Right-click the Security key, select New, and then select DWORD Value
iv. Type SupressNameChecks, and then press Enter
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

For Outlook 2000, do;

i. Select Start, select Run, type regedit in the Open box, and then select OK
ii. Locate the registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\9.0\Outlook\Security
If a Security registry key does not exist, create a new key. To do this, follow these steps:
a. Select the registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\9.0\Outlook
b. On the Edit menu, point to New, and then select Key
c. Type Security, and then press Enter
iii. Right-click the Security key, select New, and then select DWORD Value
iv. Type SupressNameChecks, and then press ENTER
v. On the Edit menu, select Modify
vi. Type 1, and then select OK
vii. On the Registry menu, select Exit

In order to ensure that a certificate has been associated with a contact in Outlook, we follow these steps:

1. Open the signed e-mail message received from the recipient
2. From the subject line of that signed email, right click and select ‘Add to Contacts’
3. If the sender is not in our address book, a Contact window will appear. Enter the details
4. Once added click Save and Close. This automatically adds the sender’s Digital ID
5. If the sender is already present in our contact book, a dialog box will show as duplicate contact, click OK to update the new information.

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