Skip to main content

Knowledge Base

Everyday Uses for Sieve Mail Filters in Zimbra

Sieve is not only for sorting newsletters. The same filters that tidy a mailbox also warn users about phishing, quiet down automated alerts and keep a shared address organized. Here are ten jobs Sieve does on a Zimbra server every day, each one covered in its own article.

New to Sieve? Start with Zimbra Sieve Filters: An Introduction, or jump straight to 10 Zimbra Sieve Filter Examples for scripts you can copy.

1. Tag external mail so people stay cautious​

In most mail clients a message from outside your organization looks exactly like one from a colleague. A domain-wide filter that marks external mail with [EXTERNAL] gives every user a reason to slow down before they trust a request.

2. Flag senders who impersonate your colleagues​

Invoice fraud usually arrives as a familiar display name attached to an unfamiliar address. Sieve can compare the two and flag any message where the name matches a member of staff but the domain does not.

3. File suspected spam by its spam score​

Zimbra's spam filter writes its verdict into the message headers instead of deciding what happens next. Reading that score in Sieve lets you send borderline mail to a review folder while obvious spam goes straight to Junk.

4. Block a sender or a whole domain​

Some senders keep writing long after you have asked them to stop. A short blocklist filter discards or rejects their mail before it ever reaches the Inbox, for one address or for an entire domain.

5. Sort mailing lists and newsletters out of the Inbox​

Bulk mail carries headers that ordinary correspondence does not, so it can be recognized without naming a single sender. One rule moves every list and newsletter into folders you read when it suits you.

6. Separate mail sent to you from mail you are only copied on​

A message addressed directly to you usually needs an answer, and a message you were copied on usually does not. Splitting the two turns the Inbox into a list of things that actually need your attention.

7. Give every service its own plus address​

Signing up as you+shop@example.com still delivers to your mailbox, and Sieve can file each variant in its own folder. When one of those addresses starts receiving spam, you know exactly who leaked it.

8. File or reject mail by attachment​

Sieve on Zimbra can test whether a message has an attachment at all and what the file is called. That is enough to route contracts and scans to the right folder, or to refuse executable files at delivery.

9. Answer automatically while you are away​

Zimbra does not implement the RFC 5230 vacation extension, so a Sieve auto-reply uses its own reply action, which answers every message that matches. Knowing that is what keeps an out-of-office rule from arguing with a mailing list.

10. Keep automated alerts and reports out of the Inbox​

Monitoring systems, backup jobs and cron scripts send mail that matters only when something is wrong. Filing the routine notifications and leaving the failures in the Inbox means you notice the ones that count.

Where to go next​

Each of these use cases gets its own article with a complete script and the Zimbra-specific details. In the meantime, Zimbra Sieve Filters: An Introduction explains where Zimbra stores Sieve scripts and how to apply them to one user or a whole domain.