How to Create Email Filter Rules in ISPConfig

This guide shows you how to create email filter rules for a mailbox in the ISPConfig control panel on your Noiz hosting account. Filter rules (sometimes called message rules, sorting rules or Sieve filters) run on the server the moment a message arrives, before any mail programme sees it, and can move the message to a folder, delete it, keep it in the Inbox, or reject it back to the sender based on its subject, sender, recipient, mailing list ID, any other header, or its size. Because the rules live on the server, they work the same whether you read your mail in webmail, on your phone or on your computer.

Last reviewed: 27 July 2026, against ISPConfig 3.3.1p1. This article follows the official ISPConfig manual procedure for creating email filter rules, cross-checked against the current interface. ISPConfig evolves between releases, so if a screen differs from this guide, check the official documentation links below.

Official Documentation Reference

• ISPConfig official documentation index
• ISPConfig 3 documentation: Basic Email Configuration
• ISPConfig 3 documentation: My First Email

Prerequisites

• You can log in to the ISPConfig control panel.
• The mailbox you want to filter already exists. If not, first create an email mailbox in ISPConfig.
• You read the mailbox over IMAP, either in webmail or in a mail programme set up with IMAP. Folders other than the Inbox are only visible over IMAP; POP3 downloads the Inbox alone, so mail filtered into folders would seem to vanish.

How Filter Rules Work

• Rules belong to one mailbox. Each mailbox on your domain has its own independent set of filter rules.
• Rules only apply to mail that arrives after the rule is saved. Messages already sitting in the mailbox are not sorted retroactively.
• Rules are checked one after the other. A rule that moves, deletes or rejects a message ends processing for that message; later rules do not run on it. Newly added rules are placed at the top of the processing order. The list on the Mail Filter tab is sorted by rule name, so it does not show the order in which rules run.
• A message that matches no rule is delivered to the Inbox as normal.

Open the Mail Filter Tab

1. Log in to the ISPConfig control panel.
2. Click the Email tab in the top navigation bar.
3. In the left-hand menu, under Email Accounts, click Email Mailbox. The list of mailboxes on your account appears.
4. Click the mailbox you want to add filters to, for example [email protected]. The mailbox settings open with the tabs Mailbox, Autoresponder, Mail Filter, Custom Rules and Backup. Custom Rules is only visible to the server administrator, so it does not appear on a hosting account, and Backup is not shown on every account either.
5. Click the Mail Filter tab.

Besides the list of filter rules, this tab holds three built-in housekeeping settings for the mailbox:

• Move Spam Emails to Junk folder.: controls what happens to messages the server-side spam filter has tagged as spam. Move first, before custom filters. puts tagged spam into the Junk folder before your own rules run (the usual choice), Move last, after custom filters. lets your own rules see the message first, and Do not move Spam Emails to Junk folder. leaves tagged spam in the Inbox. This only has an effect while the spam filter is active for the mailbox or its domain, and the Junk folder is only visible over IMAP.
• Purge Trash automatically after X days: automatically empties the Trash folder of items older than the number of days you enter. 0 disables the purge.
• Purge Junk automatically after X days: the same automatic clean-up for the Junk folder. 0 disables it.

Create a Filter Rule

Step 1: Add a new filter

1. On the Mail Filter tab, click the Add new Filter button. The Email filter form opens on its Filter tab.
2. In the Name field, type a short label that reminds you what the rule does, for example Newsletters or Invoices to folder. The name is only for you; it does not affect matching.

Step 2: Set the Source (what to match)

The Source section has three parts stacked under one another: which part of the message to examine, how to compare it, and the text to look for.

1. In the first drop-down, choose the part of the message to examine:
   • Subject: the subject line.
   • From: the sender.
   • To: the recipient address the message was sent to. Useful when several addresses deliver into one mailbox.
   • List ID: the mailing list identifier that most newsletter and discussion list software adds, for example customers.lists.example.com.
   • Header: any other message header of your choice.
   • Email size over (KB): the overall size of the message.
2. In the second drop-down, choose the condition: Contains, Is, Begins with, Ends with, Matches Regex (POSIX), Localpart or Domain.
   • Contains is the safest everyday choice, and matching is not case sensitive. For From and To in particular, prefer Contains over Is: the header usually reads Jane Doe <[email protected]>, so an exact Is match on just the address fails. With Contains you can match either the address or the display name.
   • Localpart and Domain match exactly the part of an email address before or after the @ sign, and are meant for the address fields From and To. For example, From plus Domain plus example.com matches every sender at that domain.
   • Matches Regex (POSIX) is for advanced patterns. It uses POSIX extended syntax; inline flags such as (?i) are not supported, so for case-insensitive matching use Contains instead, or character classes such as [aA][bB][cC].
3. In the text field, type the search term, for example invoice for a subject rule or [email protected] for a sender rule. Two sources need a special format here:
   • With Header, type the header name, a colon, then the text to look for, for example X-Mailer: ExampleApp.
   • With Email size over (KB), type the size, adding k after the number for kilobytes, for example 500k. A plain number is treated as megabytes, so 10 matches messages larger than 10 MB. The condition drop-down has no effect for size rules; the rule always matches messages larger than the size given.

Step 3: Choose the Action (what to do with matches)

1. In the Action drop-down, choose what happens to messages that match:
   • Move to: files the message into the folder you name in the text field below the drop-down, then stops further rules. Type the folder name exactly, for example Newsletters; use / for a subfolder, for example Work/Invoices. Folder names may only contain letters, numbers and the characters - . _ & / and spaces. Create the folder in webmail or your IMAP mail programme first if it does not already exist.
   • Delete: discards the message permanently. The sender is not notified and the message does not appear in Trash, so use this with care; moving suspect mail to a folder you review is usually safer.
   • Keep: delivers the message to the Inbox and protects it, so a later rule cannot delete it. Unlike the other three actions, Keep does not end processing, so later rules still run against the message. Use it as an exception near the top of your rules, for example to keep mail from an important sender that a broader rule further down would otherwise remove.
   • Reject: refuses the message and returns it to the sender. In this case the text field below the drop-down holds the short rejection note sent back, for example Not accepted at this address, not a folder name.
2. Leave the Active box ticked so the rule takes effect. Unticking it later switches the rule off without deleting it.
3. Click Save. You are returned to the Mail Filter tab and the new rule appears in the list.

Step 4: Test the rule

1. Wait a minute or two: ISPConfig applies changes to the mail server on a short cycle, so a brand-new rule may not take effect instantly.
2. Send the mailbox a test message that matches the rule, for example one with the search term in the subject line.
3. Check the result in webmail or an IMAP mail programme: the message should be in the target folder (or absent, for a delete rule) rather than in the Inbox.

Edit, Disable or Remove a Rule

• To change a rule, open the mailbox, go to the Mail Filter tab and click the rule's name in the list. Adjust the fields and click Save.
• To pause a rule without losing it, open the rule, untick Active and save.
• To remove a rule permanently, click its Delete button in the list and confirm.

Troubleshooting

• Filtered messages seem to have disappeared: your mail programme is probably using POP3, which only sees the Inbox. Log in to webmail, or set the account up with IMAP, and the folders your rules file into will appear. You may also need to subscribe to the folder in your mail programme's folder list.
• Moved messages land in the Inbox instead of the folder: the target folder does not exist or its name is spelt differently. Create the folder in webmail with exactly the name used in the rule, including capitalisation, then test again.
• The rule never matches: switch the condition to Contains and simplify the search term. Remember that From headers usually include a display name around the address, that filters only act on newly arriving mail, and that changes take a minute or two to reach the mail server.
• Spam is not being moved to Junk: check that Move Spam Emails to Junk folder. is not set to Do not move Spam Emails to Junk folder., and that the Spamfilter setting on the Mailbox tab is on a level other than Uncensored, which switches the spam filter off. The level can be set on the mailbox itself or on its mail domain. Only messages the filter has tagged as spam are moved.
• Error "The max. number of mailfilters is reached.": your hosting plan's filter limit is full. Delete a rule you no longer need, or open a support ticket with the Noiz support team to discuss raising the limit.
• Error "The target may only contain these characters: a-z, 0-9, -, ., _, &, /, and {space}": the folder name contains a character ISPConfig does not accept. Rename the target using only letters, numbers and the listed characters.
• A correspondent says their mail bounced back: a Reject rule matched their message. Review your rules and loosen or deactivate the one responsible.

If you get stuck at any point, open a support ticket with the Noiz support team and include the mailbox address, the rule's Source, condition, search term and Action exactly as saved, and an example message (sender, subject and approximate time) that the rule handled incorrectly.