Where to go to fix end user Secure Message account issues?

The end user guide for receiving Secure Messages (https://docs.sophos.com/central/Secure/Help/en-us/central/Secure/concepts/EncryptedPdfMessages.html) tells the recipient several times if they have issues, to contact the organization (us) sending the message.

Examples:

• If you enter an incorrect username or password three times, for security reasons you are locked out of your account. If this happens you must contact the organization that sent you the encrypted email.
• If you have trouble recovering your password you must contact the organization that sent you the encrypted email.

As the IT administrators/support for the "organization" responsible for the secure messages being sent out, where do we go to resolve these issues that the end users have? How do we fix their issues and reset the external recipient accounts?

Thanks