`sig
exception Protocol_error
exception Transient_error of int * string
exception Permanent_error of int * string
val tcp_port : int
class client :
Netchannels.in_obj_channel ->
Netchannels.out_obj_channel ->
object
method data : Netchannels.in_obj_channel -> unit
method expn : string -> string list option
method helo : ?host:string -> unit -> string list
method help : unit -> string list
method mail : string -> unit
method noop : unit -> unit
method quit : unit -> unit
method rcpt : string -> unit
method rset : unit -> unit
end
end`