The SMTP to FlowingMail gateway is a server that is installed between the office SMTP server and the internet (firewall). For each outgoing email that is sent to a recipient for which a FlowingMail address is registered the gateway send the mail using the FlowingMail protocol instead of the SMTP. The opposite is done for incoming mails: each incoming FlowingMail message is transformed into a normal email and sent to the company SMTP server.