Every time you open a terminal, it greets you with:

You have mail.

You type mail, expecting some exciting cron failure notification, and get:

No mail for <username>

Cool. Thanks, computer.

TL;DR

The file /var/mail/<username> exists (maybe even empty or corrupted). The login shell sees it and tells you "You have mail." But mail can't parse it as a valid mailbox, so it says there's nothing.

The Case

This happens on macOS when some process writes to /var/mail/<username> — usually cron or a system daemon. The file gets created, but either the content is malformed, or it's been partially consumed by another process. What's left is a file that exists (so login flags it) but contains no parseable mail (so mail has nothing to show).

The Digging

Step 1: Check if the file exists

ls -la /var/mail/$(whoami)

In my case:

-rw-------@ 1 <username>  mail  1 Mar 26 23:13 /var/mail/<username>

1 byte. That's it. A single byte of nothing useful.

Step 2: Try to read it

cat /var/mail/$(whoami)

No output. The file exists but is effectively empty.

Step 3: Check the mail queue

mailq

postqueue: fatal: Queue report unavailable - mail system is down

The mail system (Postfix) isn't even running. Which makes sense — nobody actually uses local mail on a Mac.

Solution

Clear the file:

> /var/mail/$(whoami)

Verify:

ls -la /var/mail/$(whoami)
-rw-------@ 1 <username>  mail  0 Mar 27 02:18 /var/mail/<username>

0 bytes. Restart your terminal — no more "You have mail."

Why This Keeps Happening

Something on your system periodically writes to /var/mail/<username>. If you want to find the culprit next time, run:

crontab -l

Or check system-level crons:

ls /etc/cron.d/
ls /etc/periodic/

Honestly though, on a dev machine you probably don't care. Just clear the file when it shows up again, or add > /var/mail/$(whoami) to your .zshrc if it really bothers you. Not the cleanest fix, but who cares — it's local mail on macOS. Nobody is using it.