Among Slrn's most impressive features is its scorefile capability. It uses a syntax that mere humans can decipher, and it can be used with virtually any header or fragment. The included slrnpull utility simulates a small server spool on the local machine. Also, support is included for reading from a real news spool and posting via inews.
Mail sending is extremely flexible, allowing any program to be substituted for sendmail.
Hooks are provided to allow any text editor or script to be used for composing articles, and incoming articles are easily archived or piped to external commands. Good support is included for multiple servers and configurations, but only one server per invocation. Especially nice is the ability to reconstruct threads. S-Lang macros allow Slrn to gain new features or emulate the interfaces of other programs. Though Slrn fails 12c, I consider that a feature.