Lines of smtp2tg.toml.example from check-in f5ed284f8c that are changed by the sequence of edits moving toward check-in 14ef340959:

                         1: # vi:ft=toml:
                         2: # Telegram API key
                         3: api_key = "YOU_KNOW_WHERE_TO_GET_THIS"
                         4: 
                         5: # where to listen on (sockets are not supported since 0.3.0)
                         6: listen_on = "0.0.0.0:25"
                         7: 
                         8: # whether we need to handle unknown adresses
                         9: # - relay: send them to default one
                        10: # - deny: drop them
                        11: unknown = "relay"
                        12: 
                        13: # default fields to show in message header
                        14: fields = [ "date", "from", "subject" ]
                        15: 
                        16: # which domains are allowed in addresses
                        17: # this means that any unqualified recipient "somebody" will also match
                        18: # to "somebody@each_domain"
                        19: domains = [ "localhost", "current.hostname" ]
                        20: 
                        21: # default recipient, should be specified
                        22: # still can be a user, channel or group
                        23: default = 0
                        24: 
                        25: [recipients]
                        26: # make sure you quote emails, as "@" can't go there unquoted. And by default
                        27: # we need FQDNs
                        28: "somebody@example.com" = 1 # user id's are positive
                        29: "root" = -1 # group id's are negative
                        30: 
                        31: # to look up chat/group id you can use debug settings in Telegram clients,
                        32: # or some bot like @getidsbot or @RawDataBot