T.37 is the ITU store-and-forward standard for sending faxes in e-mail. Store-and-forward fax breaks the fax process into distinct sending and receiving processes and allows fax messages to be stored between those processes. Store-and-forward fax also enables fax transmissions to be received from or delivered to computers rather than fax machines. Store-and-forward can exploit all the flexibility of e-mail, such as sending to distribution lists.

Store-and-forward lets you set up mail servers to try continuously, so the sending user never sees a busy signal. You can use all the features implicit in e-mail, such as distribution lists that send traffic to multiple fax machines. Synchronization would be very difficult for real-time among multiple destinations. If transmission is delayed until idle time, and the enterprise is already connected to the Internet, long-distance charges for fax disappear.

Almost any Internet connection will be faster than 14.4Kbit/sec. or 34Kbit/sec. fax. The biggest problem is that store-and-forward doesn't implicitly link transmission and reception, so there could be a problem if receipt confirmation is needed in real time.

Receiving fax as e-mail is especially attractive to remote workers. A traveling worker with a virtual private network (VPN) connection also can send through the company's fax servers.

-- On-ramp -- Store-and-forward uses an on-ramp gateway to get onto the Internet, sending TIFF images as e-mail attachments. Obviously, there must be a SMTP server between the PC that creates the TIFF file and the fax gateway router. There are physical fax machines than handle documents in the traditional way, but connect via the T.37 store-and-forward technique rather than analog. Such machines may also have a backup G3 interface, or you can use a commercial service that accepts TIFF e-mail and sends it to G3 analog machines.