environment variables)
```
-% REMOTE_IMAP_DOMAIN=imap.coolmailsite.example REMOTE_SMTP_DOMAIN=smtp.coolmailsite.example olden-mail
+% REMOTE_IMAP_HOST=imap.coolmailsite.example REMOTE_SMTP_HOST=smtp.coolmailsite.example olden-mail
```
+## Middleware
+
+In order to work with some older clients, middleware allow transformation of
+messages. The current middleware are:
+
+- `FindMailboxesCompatibility` - Transforms IMAPv3 FIND MAILBOX commands to
+ IMAPv4 LIST commands.
+
## Debugging
You can control how much it prints by setting `RUST_LOG`. Setting it to
`debug` will output the whole protocol stream. The default level is
`info`.
+
+Messages coming from the client are prefixed with `>>>`, and messages coming
+from the server with `<<<`. If a middleware modified a command, you'll see
+the message that was actually sent prefixed with `###`.