When using Epson Device Admin, you can set the IP fax settings on multiple printers as a batch.
For details, see the manual or help for Epson Device Admin.
Operation Flow of Epson Device Admin
Enabling Sending and Receiving IP Faxes on an Intranet (Intranet Settings) <Epson Device Admin>
Enabling Sending and Receiving IP Faxes Using G3 Fax-compatible Devices (Through a VoIP Gateway) <Epson Device Admin>
Setting Items for IP-FAX Settings > VoIP Gateway Settings <Epson Device Admin>
Registering a VoIP Gateway <Epson Device Admin>
Priority Settings for VoIP Gateway <Epson Device Admin>