Missing or wrong Date and Message-ID headers

What it means

Each email has hidden lines at the top called headers. Two of them are expected in every message:

• Date: when the email was written, with the time zone. Example: Date: Tue, 14 Oct 2025 09:30:00 +0200
• Message-ID: a unique identifier, like a serial number. Example: Message-ID: <7f3a91c2@mail.yourdomain.com>

Normal email programs add them automatically. They are usually missing or wrong when emails are sent by a script, a website plugin, a printer or an old application that builds the email by hand.

Why it matters

• SpamAssassin adds points for a missing date (MISSING_DATE), a missing Message-ID (MISSING_MID), or a date far in the past or future (DATE_IN_PAST_..., DATE_IN_FUTURE_...).
• Gmail can refuse emails that have no valid Message-ID, and expects messages to follow the email format standard (RFC 5322).
• Mail programs use these headers to sort messages and build conversations.

How to check

Send an email from the tool or script that has the problem to your test address on the home page (/). In the report, the SpamAssassin section lists the rules that matched. You can also open the email's original source in any mailbox ("Show original" in Gmail) and look at the first lines.

How to fix it

1. Let a mail library build the email

The best fix is to stop writing headers by hand. Libraries such as PHPMailer or Symfony Mailer (PHP), Nodemailer (Node.js) or the email module (Python) add both headers correctly. In Python, for example:

from email.utils import formatdate, make_msgid
msg["Date"] = formatdate(localtime=True)
msg["Message-ID"] = make_msgid(domain="yourdomain.com")

2. If you write headers yourself

• Date must use the exact format Day, DD Mon YYYY HH:MM:SS +ZZZZ in English, with the real time zone offset.
• Message-ID must be unique for every email, surrounded by < and >, and contain an @ followed by your domain or server name. Never reuse the same ID.
• Use only one Date and one Message-ID per email.

3. Fix the clock

A wrong date often comes from a server whose clock is off or set to the wrong time zone. On Linux, enable time synchronisation (for example with timedatectl set-ntp true) and check the time zone.

4. Let your mail server add what is missing

Some servers can add a missing Date or Message-ID for messages they send. Postfix, for example, does this for emails submitted on the server itself, but not always for emails coming from other machines. This is a safety net, not a replacement for fixing the application.

Check that it is fixed

Send a new email from the same tool to the home page address. The SpamAssassin section should no longer list MISSING_DATE, MISSING_MID or date rules, and the date shown should match the real sending time.