Man pages › Compared with Linux and the BSDs

`mailx(1)` on Solnix vs Linux and the BSDs

On Solnix, mailx is the illumos mailx at /usr/bin/mailx. It is a POSIX.1-2024 utility. Several single-letter flags differ from FreeBSD and NetBSD: -I, -r and -H mean different things, and Solnix lacks -E and -a. The Solnix system startup file also sets non-standard defaults unless you pass -n. The bundle has no Linux page.

The manual pages

Solnix: mailx(1) from pkgs.solnix.illumos-world-man · illumos.org
FreeBSD: mailx(1) 15.1-RELEASE
NetBSD: mailx(1) 11.0
Standard: POSIX.1-2024 (IEEE Std 1003.1-2024), mailx

What Solnix runs

A default Solnix system runs the illumos mailx at /usr/bin/mailx. The SYNOPSIS also lists /usr/ucb/mail and /usr/ucb/Mail, but the header says no other variants are shipped and the bundle does not describe them. When invoked as mail or Mail, it reads /etc/mail/Mail.rc instead of /etc/mail/mailx.rc.

Differences

Compared with	Topic	What differs
FreeBSD, NetBSD	system startup file sets non-standard defaults	Many Solnix administrators put set appenddeadletter, unset replyall and unset pipeignore in the system startup file for old Solaris compatibility. The page says this does not meet standards requirements. Use `-n` or a personal startup file for standard behaviour. The BSD excerpts describe no such split. Source: Solnix mailx(1) USAGE, Starting Mail; -n
NetBSD	`-I` meaning	Solnix `-I` includes newsgroup and article-id header lines when printing, and requires `-f`. NetBSD `-I` forces interactive mode even when input is not a terminal. On Solnix the equivalent for tilde escapes is -~. Source: Solnix mailx(1) -I, -~; NetBSD mailx(1) -I
NetBSD	`-r` meaning	Solnix `-r` address sets the return address passed to the delivery program and disables all tilde commands. NetBSD `-r` names an alternate rcfile that overrides MAILRC and ~/.mailrc. Source: Solnix mailx(1) -r; NetBSD mailx(1) -r
NetBSD	`-n` and the startup file location	Solnix `-n` skips the system file `/etc/mail/mailx.rc` (or Mail.rc); $HOME/.mailrc is then still the personal file. NetBSD `-n` skips `/etc/mail.rc.` The Solnix excerpt does not mention a MAILRC variable. Source: Solnix mailx(1) -n, USAGE Starting Mail; NetBSD mailx(1) -n, -r
FreeBSD, NetBSD	`-E` missing	The FreeBSD and NetBSD synopses have `-E`. NetBSD documents it as not sending messages with an empty body, useful for cron error pipes. Solnix has no `-E`. Solnix `-e` is a different flag: it tests whether mail exists. Source: NetBSD mailx(1) -E; FreeBSD mailx(1) SYNOPSIS; Solnix mailx(1) -e, SYNOPSIS
NetBSD	attachments	NetBSD mail `-a` attaches a file to the message. Solnix mailx has no `-a` in its synopsis or options. Source: NetBSD mailx(1) -a; Solnix mailx(1) SYNOPSIS, OPTIONS
NetBSD	`-H` behaviour	Solnix `-H` prints the header summary only. NetBSD `-H` takes an optional colon-modifier, such as `-H`:n for new messages, and exits. The FreeBSD `-H` text is not in the bundle. Source: Solnix mailx(1) -H; NetBSD mailx(1) -H; FreeBSD mailx(1) SYNOPSIS
NetBSD	`-u` user	Solnix `-u` reads the named user's mailbox, but only if it is not read protected. NetBSD `-u` is documented as equivalent to mail `-f` `/var/mail/user.` Source: Solnix mailx(1) -u; NetBSD mailx(1) -u
FreeBSD, NetBSD	Solnix-only options	Only Solnix documents `-t` (take recipients from To:, Cc: and Bcc: in the input), `-h` number (hop count), `-T` file, `-U` (convert UUCP addresses), `-B` (unbuffered I/O) and `-V` (print version). Source: Solnix mailx(1) -t, -h, -T, -U, -B, -V; FreeBSD and NetBSD mailx(1) SYNOPSIS
FreeBSD, NetBSD	passing options to sendmail	FreeBSD and NetBSD synopses accept sendmail options after the recipients. NetBSD says they are passed directly to sendmail. The Solnix synopsis has no such trailing options. It passes only `-v` to sendmail(8), and `-r` and `-h` to the delivery program. Source: FreeBSD mailx(1) SYNOPSIS; NetBSD mailx(1) Sending mail; Solnix mailx(1) -v, -r, -h
FreeBSD	environment variables	The FreeBSD page documents DEAD (default ~/dead.letter), MAIL (default `/var/mail`), MAILRC (default ~/.mailrc), LISTER, PAGER, REPLYTO and others. The Solnix excerpt in the bundle shows only MBOX, the mbox file in HOME, so compare its full ENVIRONMENT VARIABLES section before relying on these. Source: FreeBSD mailx(1) ENVIRONMENT; Solnix mailx(1) DESCRIPTION (MBOX)
FreeBSD, NetBSD	command names	FreeBSD documents mail, Mail and mailx, and notes that mail is usually a link to Mail and mailx. NetBSD documents mail and mailx. Solnix lists `/usr/ucb/mail` and `/usr/ucb/Mail` as alternate names, and mail or Mail selects `/etc/mail/Mail.rc.` Source: FreeBSD mailx(1) NAME, BUGS; NetBSD mailx(1) NAME; Solnix mailx(1) SYNOPSIS, USAGE

Standards

POSIX: mailx is a POSIX.1-2024 utility.
Solnix: The USAGE section says the Solaris-compatible system startup defaults (appenddeadletter, no replyall, no pipeignore) do not meet standards requirements for mailx. Use -n for standard behaviour.

Writing portable scripts

Always run mailx -n in scripts on Solnix, so the system startup file cannot change replyall, pipeignore or appenddeadletter behaviour.
Avoid -I, -r, -H, -E and -a in portable scripts. They mean different things, or are missing, between Solnix, FreeBSD and NetBSD. Use only -s, -c, -b and plain recipients.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.