Notmuch Emacs interface vs S-nail

Notmuch Emacs interface: Emacs front end for notmuch that reads, searches, tags and composes mail from a local Maildir.
S-nail: Command-line mail program that implements POSIX mailx, with MIME, IMAP, POP3, SMTP, Maildir and S/MIME support.

Differences

Notmuch Emacs interface is a mail client that runs inside Emacs; S-nail is a command-line program.
Only Notmuch Emacs interface has built-in notmuch.
Only S-nail has built-in IMAP, POP3 and mbox.
On Android, Notmuch Emacs interface runs through Termux and S-nail is not available.
Notmuch Emacs interface has mouse support; S-nail does not.
Notmuch Emacs interface has calendar support; S-nail does not.
Notmuch Emacs interface has OpenPGP; S-nail does not.
Notmuch Emacs interface is written in Emacs Lisp; S-nail in C.
Configuration: Notmuch Emacs interface uses Emacs Lisp in init.el plus the notmuch config file, and S-nail uses ~/.mailrc command file.

Side by side

	Notmuch Emacs interface	S-nail
Interface	Runs inside Emacs	Command-line tools and prompts
Language	Emacs Lisp	C
License	GPL 3.0 or later	ISC and BSD 2-Clause and BSD 3-Clause and BSD 4-Clause
Latest version	`0.40`	`14.9.25`
Linux	Native	Native
macOS	Native	Native
Windows	Through WSL	Through WSL
BSD	Native	Native
Android	Through Termux	No
IMAP	Through a separate tool	Yes
POP3	Through a separate tool	Yes
SMTP	Yes	Yes
JMAP	No	No
Maildir	Yes	Yes
mbox	No	Yes
notmuch	Yes	No
OpenPGP	Yes	No
S/MIME	Yes	Yes
OAuth2 sign-in	via script	via script
Threads	Yes	Yes
Search	notmuch Xapian full-text search with tags	built-in message specifications and the search command; IMAP SEARCH on IMAP folders
HTML mail	built-in, rendered with the Emacs shr library	built-in tag-soup filter or external viewer via mailcap
Mouse	Yes	No
Multiple accounts	Yes	Yes
Offline use	full; reads a local Maildir synced by mbsync or OfflineIMAP	IMAP cache with disconnected mode
Calendar	shows text/calendar parts; no invitation replies	No
Contacts	address completion from the notmuch index	aliases via the alias command
Vim-style keys	No	No
Configuration	Emacs Lisp in init.el plus the notmuch config file	~/.mailrc command file

Which to choose

Choose Notmuch Emacs interface for

Tag-based organization with fast full-text search over all local mail.
Shows a whole thread in a single buffer.
Handles PGP/MIME and S/MIME signatures and decryption through notmuch.

Watch out for

No built-in IMAP; needs mbsync or a similar sync tool.
Custom tags stay in the local index; only standard flags such as unread and replied reach the IMAP server.
Requires Emacs and some Emacs Lisp to configure.

Install Notmuch Emacs interface

Choose S-nail for

Drop-in POSIX mailx, so it works in existing shell scripts and cron jobs.
Built-in SMTP, POP3 and IMAP with TLS; no separate sync or send tool needed.
S/MIME signing and encryption are built in.

Watch out for

Line-oriented prompt instead of a full-screen interface.
No built-in OpenPGP; upstream documents a gpg pipe workaround only.
IMAP support is kept at an older code level and upstream advises care.

Install S-nail

Questions

What is the difference between Notmuch Emacs interface and S-nail?

Notmuch Emacs interface is a mail client that runs inside Emacs; S-nail is a command-line program. Only Notmuch Emacs interface has built-in notmuch. Only S-nail has built-in IMAP, POP3 and mbox.

Which runs on Windows, Notmuch Emacs interface or S-nail?

On Windows, Notmuch Emacs interface runs through WSL. On Windows, S-nail runs through WSL.