Dear fellow Haskellers, I have written an SMTP server (Main.hs at http://hpaste.org/56134, full git repo at http://strake.zanity.net:1104/ymail.git), which works, mostly – it responds to every message with that it was sent properly, whether it was or not. (Try it: send an e-mail by SMTP to this_is_not_a_user@strake.zanity.net or somesuch.) The reason is, that it simply tells the message (envelope, data) in a Writer monad, which is later piped to the local delivery agent. As I said, this works, but of course is suboptimal. I tried to change the type of main_ to (MonadState MTPState m, MonadIO m) => [Char] -> m ([Char], [Char]), just calling LDA in main_ (when mode is MTPTextMode) rather than after, but then the program output nil. I'm not sure what the problem is – I thought IO might not be lazy enough so I tried a lazy wrapped-IO monad, in vain. How, then, can this program call the LDA, wait to know whether it worked or failed, and then respond? Thanks for any help. Cheers, M Farkas-Dyck