plain:
  driver                     = plaintext
  public_name                = PLAIN  
  server_set_id              = $auth2
  server_prompts             = :
  server_condition           = ${if saslauthd{{$ 2 }{$ 3 }{smtp}} { 1 }}
#  server_advertise_condition = ${if def:tls_cipher }

# LOGIN authentication has traditional prompts and responses. There is no
# authorization ID in this mechanism, so unlike PLAIN the username and
# password are $auth1 and $auth2. Apart from that you can use the same
# server_condition setting for both authenticators.

login:
  driver                     = plaintext
  server_set_id              = $auth1
  server_prompts             = <| Username: | Password:
  server_condition           = ${if saslauthd{{$ 1 }{$ 2 }{smtp}} { 1 }}
#  server_advertise_condition = ${if def:tls_cipher }

$ telnet server.example  25 
Trying  192 . 168 . 34 . 25 ...
Connected to server.example.
Escape character is ’^]’.
 220  server.example ESMTP Exim  4 . 20  ...
ehlo client.example
 250 -server.example Hello client.example [ 10 . 8 . 4 . 5 ]
 250 -SIZE  52428800 
 250 -PIPELINING
 250 -AUTH PLAIN
 250  HELP