Standard SMTP over tcp
val with_ : (?config:Client_config.t ‑> ?credentials:Types.Credentials.t option ‑> log:Mail_log.t ‑> ?flows:Mail_log.Flows.t ‑> ?component:Mail_log.Component.t ‑> Types.Address.t ‑> f:(t ‑> 'a Async.Deferred.Or_error.t) ‑> 'a Async.Deferred.Or_error.t) Async.Tcp.with_connect_options