This is a sequel to "Postfix: relay to authenticated SMTP".
I would like to send mail from two different Gmail accounts using Postfix. Here is the relevant section in the Postfix documentation: Configuring Sender-Dependent SASL authentication.
As a concrete example, here's how to set up two Gmail accounts (only relevant sections of the config files are listed below):
/etc/postfix/main.cf: # sender-dependent sasl authentication smtp_sender_dependent_authentication = yes sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay