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Every message that lands in your Inbox is checked on arrival, and the ones that need attention today get an Urgent badge and a louder notification. Out of the box Mermail uses a sensible built-in definition of urgent. When that definition does not match how you work, you can replace it with your own rules, written in plain language. This guide shows both: what the built-in behavior does, and how to write a custom rule. The example rule is one line — emails from a specific client are always urgent — and you will see it take effect on the next message that arrives.

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What you need

  • A mailbox you can open in the Mermail console.
  • A few minutes to think about what “urgent” actually means for this mailbox. That is the real work here; typing the rule takes seconds.

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Open the setting

Click the gear icon beside the mailbox name to open Settings, then scroll to Urgent email detection. The badge next to the section title tells you the current state at a glance:
Mermail mailbox settings showing Urgent email detection with the Custom rules badge, the enable toggle, and a custom urgency rule

The Urgent email detection section, with a custom rule saved.

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Start with the built-in rules

If you leave Custom urgency rules empty, Mermail applies its own definition. Click View built-in default rules to read them in full. In short, a message is marked urgent when it needs attention today — blocked customers, outages, payment failures, explicit deadlines, angry escalations, or time-sensitive requests from important contacts. Newsletters, FYI updates, marketing, routine notifications, “when you have a chance” requests, and automated reports are not urgent.
Most mailboxes can leave the custom rules empty. Write your own only when the built-in definition misses something specific to your work, or flags things you do not care about.

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Write your own rules

1

Make sure detection is on

Enable urgent email detection must be toggled on. While it is off, the rules field is disabled and nothing is ever marked urgent.
2

Write the rules

Type your rules into Custom urgency rules (optional), one rule per line. Say who or what is urgent, and be specific about the sender, domain, subject, or content that should match.
You can combine several rules, and you can state exceptions:
The field holds up to 2,000 characters.
3

Save

Click Save Changes. Changes saved appears beside the button and the badge at the top of the section switches to Custom rules. The next message that arrives is checked against your rules.
Custom rules fully replace the built-in defaults. Once you save a rule, outages and deadlines are no longer urgent unless your own rules say so. If you want the built-in behavior plus something extra, write out both.

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What happens when mail arrives

A message that matches your rules is flagged the moment it lands. In the inbox list it carries an Urgent badge alongside its other labels.
Mermail inbox list with an email showing an Urgent badge next to its Partnership and UIUX labels

An incoming message from the sender named in the rule, flagged Urgent in the inbox list.

Open the message and the badge stays with the thread, next to its labels in the header.
Opened email thread titled Re: Invite you to design my app with an Urgent badge in the header

The Urgent badge follows the thread, so the flag is still visible while you read.

Urgent mail is also announced more loudly than ordinary mail: the in-app notification is styled as an alert rather than a quiet info message, and push and Telegram notifications are marked as urgent when you have them connected.
Only incoming Inbox mail is checked. Messages you send, and mail that never reaches the Inbox, are never marked urgent.

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How Mermail decides

Knowing the decision rules makes it much easier to predict the result:
  • A rule that names a sender or domain applies only to that sender or domain. “Emails from [email protected] are urgent” never makes [email protected] urgent.
  • No clear match means not urgent. Mermail does not stretch a rule to cover something similar.
  • Ambiguity resolves to not urgent. Vague wording such as “important stuff is urgent” will mostly produce nothing at all.
  • Your rules are the only criteria. With custom rules saved, Mermail deliberately ignores general email-triage instincts such as outages, deadlines, or angry tone unless you named them.

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Write rules that work

  • Name the thing that matches — a sender address, a domain, a subject phrase, or specific content — instead of describing a feeling.
  • Say what is not urgent too. Exceptions are what keep the badge meaningful.
  • Avoid “all”, “every”, and “always urgent” on their own. If your rules look like they will flag most of your mail, Mermail asks you to confirm before saving, because badges and alerts stop being useful when everything carries them.
  • Review after a week. If nothing was flagged, your rules are probably too narrow or too vague. If everything was flagged, they are too broad.
The guiding line is printed right under the toggle: be specific — if everything is urgent, nothing is.

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Turn it off or start over

  • Reset to default appears in the section header once you have custom rules. It clears the rules field and puts the mailbox back on the built-in defaults. Save afterwards to apply it.
  • Toggle off stops detection entirely. No message is marked urgent, no badges appear, and no urgent alerts are sent. Your saved rules are kept, so you can switch it back on later.

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