@menu
* Occasional connection to mail server: UsecaseMail.
+* Lightweight fast POP3/IMAP4 replacement: UsecasePOP.
* Unreliable/expensive communication link: UsecaseUnreliable.
* Slow/expensive link for high-volume data, bad QoS: UsecaseQoS.
* Extreme terrestrial environments, no link: UsecaseNoLink.
will call local @command{sendmail} command to deliver them just like
that happened on the same machine.
+@node UsecasePOP
+@section Lightweight fast POP3/IMAP4 replacement
+
+@ref{nncp-daemon} can be connected with @ref{nncp-caller} for a long
+time -- it can create TCP connection that lasts for many hours. When
+SMTP server receives mail, it will call @ref{nncp-mail} creating an
+outbound encrypted packet. Daemon checks outbound directory each second
+and immediately sends notification about undelivered packets to remote
+side, that also downloads it at once.
+
+There are only dozens of bytes notifying about incoming packets, dozens
+of bytes telling to download those packets. Mail packets are compressed
+(POP3 and IMAP4 as a rule do not). You have lightweight, compressed,
+low-delay, reliable link for the mail with strong encryption and mutual
+sides authentication!
+
@node UsecaseUnreliable
@section Unreliable/expensive communication link
The most popular cryptographic protocol in Internet is
@url{https://en.wikipedia.org/wiki/Transport_Layer_Security, TLS} that
-is very hard to implement right and hard to configure for mutual
+is very hard to implement correctly and hard to configure for mutual
participants authentication. Not all TLS configurations and related
protocols provide @url{https://en.wikipedia.org/wiki/Forward_secrecy,
forward secrecy} property -- all previously intercepted packets could be