Lines of smtp2tg.toml.example from check-in 2158b44929 that are changed by the sequence of edits moving toward check-in f5ed284f8c:

                         1: # Telegram API key
                         2: api_key = "YOU_KNOW_WHERE_TO_GET_THIS"
                         3: 
                         4: # where to listen on (sockets are not supported since 0.3.0)
                         5: listen_on = "0.0.0.0:25"
                         6: 
                         7: # whether we need to handle unknown adresses
                         8: # - relay: send them to default one
                         9: # - deny: drop them
                        10: unknown = "relay"
                        11: 
                        12: # default fields to show in message header
                        13: fields = [ "date", "from", "subject" ]
                        14: 
                        15: # which domains are allowed in addresses
                        16: # this means that any unqualified recipient "somebody" will also match
                        17: # to "somebody@each_domain"
                        18: domains = [ "localhost", "current.hostname" ]
                        19: 
                        20: [recipients]
2158b44929 2025-06-12   21: # there should be default recipient, get's some debug info + mail that we
2158b44929 2025-06-12   22: # couldn't deliver (if enabled)
2158b44929 2025-06-12   23: _ = 1
2158b44929 2025-06-12   24: 
                        25: # make sure you quote emails, as "@" can't go there unquoted. And by default
                        26: # we need FQDNs
                        27: "somebody@example.com" = 1 # user id's are positive
2158b44929 2025-06-12   28: "root@example.com" = -1 # group id's are negative
                        29: 
                        30: # to look up chat/group id you can use debug settings in Telegram clients,
                        31: # or some bot like @getidsbot or @RawDataBot