A vFax number replaces a physical fax machine by using email to send and receive faxes using our fax gateway as a go-between your office and the sending or receiving fax machine.
T.38 Fax protocol explained
Our fax service uses the T.38 protocol to transmit faxes via the public internet. While not quite as reliable as your old PSTN fax service, you’ll find our service successfully communicates 95 of 100 fax transmissions. However, before deciding to go with our fax-mail service you should consider the following scenarios which are known to hinder transmission reliability.
- Receipt and Delivery: Ideally we recommend substituting your fax machine with your email client to both send and receive faxes.
- High Speed fax: One of the ways t.38 attempts improve IP faxing reliability is to reduce the transmission speeds down to very low baud rates (14.4kbps). The downside however is some lower cost fax machines are unable to negotiate from 56.6kbps to down to 14.4kbps causing a transmission failure.
- Colour fax: At YourCloudPBX IP faxing is black and white only. While most colour machines will negotiate down to our black and white, some machines can’t negotiate to B&W which will cause transmission failures.
- Auto Answer fax machines: We cannot communicate with fax answer machines in answer machine mode. The recipient will need to disable the answer machine to receive the incoming YourCloudPBX transmission.
If you rely on faxes as part of an emergency service or have a business process dependent on a physical fax machine for both sending and receipt we recommend retaining your legacy PSTN fax service.