By default, the Fax Voip FSP Mail to Fax subsystem is configured to be started as application under current user account. To configure Mail to Fax subsystem to be started as Windows Service, see Configure Mail to Fax as Windows Service. The service is automatically started on Windows startup, before user logon. This option is recommended for multi-user systems.
Run the service under user account
It is strongly recommended to run Fax Voip FSP Mail service on behalf of the regular user account, and not under the local system or network service accounts. There are at least two reasons for this:
Viewing and managing faxes in Windows Fax and Scan
The current user does not have access to faxes created by the other user. If the Fax Voip FSP Mail service is started under Local System account, the faxes will also be created using Local System account. You are not able to view and manage faxes in the Windows Fax and Scan application in this case. There is no normal solution to this problem. You can do certain manipulations on the Fax Properties -> Security page, but this does not solve all the problems that you will encounter. If the Fax Voip FSP Mail service is started under the specified user account, the specified user will be able to view and manage faxes generated by the service in the usual way (when logged into the system). Note that only one user (under which the service is running) can access the faxes.
Configuring file type associations
When creating a fax from your document, the Mail to Fax function trying print the document in the background using Fax printer. The success of this operation is specified by the presence of the application associated with the required file extension that should be installed and correctly registered on your computer. The associated application should support standard printto command that is used by Windows when printing a file. The file type associations, responsible for the correct printing of various documents, can be easily configured for the current user account. However, there is no easy way to configure file type associations for the local system or network service accounts. If the Fax Voip FSP Mail service is started under Local System account, the Mail to Fax function does not see your settings and usually not able to print the document. If the Fax Voip FSP Mail service is started under the specified user account, the specified user can configure file type associations in the usual way (when logged into the system).
For more details, see also the folllowing chapters of this user manual: E-mail attachments, Printto Options, To manually fix file associations in Windows 11 and Windows 10.