Forward Email vs S-nail

Forward Email: Forward Email's webmail in the terminal: mail, calendar, contacts and settings, with mouse support and a key hint bar.
S-nail: Command-line mail program that implements POSIX mailx, with MIME, IMAP, POP3, SMTP, Maildir and S/MIME support.

Differences

Forward Email is a full-screen terminal client; S-nail is a command-line program.
Forward Email connects to Forward Email accounts through its API; S-nail works with any provider over IMAP, including Forward Email.
On Windows, Forward Email runs natively and S-nail runs through WSL.
On Android, Forward Email runs through Termux and S-nail is not available.
Forward Email has mouse support; S-nail does not.
Forward Email has calendar support; S-nail does not.
Forward Email has OpenPGP; S-nail does not.
S-nail has S/MIME; Forward Email does not.
S-nail has OAuth2 sign-in; Forward Email does not.
Forward Email is written in TypeScript; S-nail in C.
Configuration: Forward Email uses settings screens, keyboard shortcut editor and an optional user.css, and S-nail uses ~/.mailrc command file.
Forward Email is source-available (Business Source License 1.1); S-nail is open source (ISC and BSD 2-Clause and BSD 3-Clause and BSD 4-Clause).

Side by side

	Forward Email	S-nail
Interface	Full-screen terminal interface	Command-line tools and prompts
Language	TypeScript	C
License	Business Source License 1.1	ISC and BSD 2-Clause and BSD 3-Clause and BSD 4-Clause
Latest version	`0.14.16`	`14.9.25`
Linux	Native	Native
macOS	Native	Native
Windows	Native	Through WSL
BSD	Native	Native
Android	Through Termux	No
IMAP	Forward Email API	Yes
POP3	Forward Email API	Yes
SMTP	Forward Email API	Yes
JMAP	Forward Email API	No
Maildir	Forward Email API	Yes
mbox	Forward Email API	Yes
notmuch	Forward Email API	No
OpenPGP	Yes	No
S/MIME	No	Yes
OAuth2 sign-in	No	via script
Threads	Yes	Yes
Search	built-in, across messages, contacts and events	built-in message specifications and the search command; IMAP SEARCH on IMAP folders
HTML mail	shown as formatted text with links; plain text by default	built-in tag-soup filter or external viewer via mailcap
Mouse	Yes	No
Multiple accounts	Yes	Yes
Offline use	drafts and changes made offline are sent when the connection returns	IMAP cache with disconnected mode
Calendar	Yes	No
Contacts	Yes	aliases via the alias command
Vim-style keys	No	No
Configuration	settings screens, keyboard shortcut editor and an optional user.css	~/.mailrc command file

Which to choose

Choose Forward Email for

Calendar, contacts and tasks in the same terminal app as mail
Mouse clicks, scrolling and text selection work, and the bottom row always shows the keys for the current screen
One self-updating executable with no setup files to write

Watch out for

Only works with Forward Email accounts
Images and video are not drawn; HTML mail is shown as text with links
Passkey sign-in needs a browser or the desktop app

Install Forward Email

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 Forward Email and S-nail?

Forward Email is a full-screen terminal client; S-nail is a command-line program. Forward Email connects to Forward Email accounts through its API; S-nail works with any provider over IMAP, including Forward Email. On Windows, Forward Email runs natively and S-nail runs through WSL.

Which runs on Windows, Forward Email or S-nail?

On Windows, Forward Email runs natively. On Windows, S-nail runs through WSL.