Create Email Rules by Sender Domain or Subject Keyword in 2026

Why filter email by sender domain or subject keyword?

You open your inbox, and 87 new messages are waiting — most from newsletters, automated alerts, and promotional blasts. You scan, sort, and delete. Again. Again. Why does it still take you 30 minutes a day just to keep up?

With 95% of people checking email five or more times daily, filtering isn’t just helpful — it’s essential. But manual sorting only delays the inevitable: missing something important from a trusted source. The real fix? Automate it — using sender domain or subject keyword rules.

These rules train your inbox to act like a smart assistant. Not based on company data mining. Not on vague AI that learns from your behavior. Just clear, user-defined logic — like "move all messages from @unifiedesk.com to a dedicated folder" or "flag anything with 'invoice' in the subject."

Key takeaways

• Sender domain filters automatically sort messages from known sources, reducing inbox clutter without relying on behavioral data collection.
• Subject keyword rules help surface high-priority messages like "payment due" or "meeting rescheduled" while hiding generic updates.
• Combining both approaches lets you build a self-hosted, privacy-preserving inbox that works on your terms — no tracking, no data harvesting.

What email rules can you create by sender domain or subject keyword?

You can automatically sort, label, flag, or delete emails based on sender domain or subject keywords. Route university emails to a dedicated folder, move invoices to Finance, auto-delete high-risk phishing messages, and mark team project emails as high priority—all with precise, configurable rules that reduce clutter and surface what matters. These rules work across your inbox, even when using mobile or desktop clients, thanks to JMAP support.

Common rule types in practice

• Route all emails from @university.edu to a folder named Education—ideal for tracking academic updates or research collaborations.
• Move any message with invoice in the subject to a Finance label, ensuring you never miss a payment or billing update.
• Auto-delete messages from unknown domains (e.g., @fake-payments.com) with urgent payment in the subject—helps block common phishing tactics without manual review.
• Tag all emails from your team’s project domain (e.g., @projectx.team) as High Priority and apply a visual priority flag—ensures you see important work immediately.

How it works under the hood

These rules are applied server-side using Sieve filters, a standardized email filtering language (defined in RFC 5228). They run every time new mail arrives, independent of your device or client. This means filtering works consistently whether you're on a phone, tablet, or desktop.

For example, you could combine domain and subject checks: if sender domain is @university.edu AND subject contains "exam schedule", then move to Education and mark as read. Rules can be nested, prioritized, and tested with real messages from your own accounts. The same filters apply when syncing via IMAP or JMAP, so your mailbox stays consistent across platforms.

While other providers like Fastmail or Proton Mail support basic filtering, Unifiedesk gives you full control over rule logic—including domain matching, case-insensitive keywords, and action chaining—without hidden limitations.

With Unifiedesk, you aren’t just filtering email—you’re building a personal inbox automation system. Want to set up rules like these? See how email works with Unifiedesk, or dive deeper into self-hosting for full control.

How do sender domain and subject keyword rules work behind the scenes?

When an email arrives, your mail server checks the 'From' header and subject line against your rules using pattern matching. If a match is found, it acts instantly—moving the message, marking it read, flagging it, or deleting it—before it ever reaches your inbox. This happens automatically, based on your preferences, protecting your time and focus.

What the server actually looks at

Every email includes metadata like the sender's domain (from the From header) and the subject line. Your mail server analyzes these elements as soon as the message lands on the server, before it is delivered to your inbox.

For example, if you've set a rule to “move all emails from @amazon.com to a folder called ‘Shopping’”, the server checks the From header against that domain. Similarly, a rule for “delete any email with ‘unsubscribe’ in the subject” checks the subject line for that keyword.

These checks are fast. They use efficient pattern-matching algorithms—common in modern mail systems and described in RFC 5322, the standard for email message syntax. The system doesn’t need to read the body; it acts on the fields that matter most for filtering.

Why it happens before inbox delivery

Rules are applied during the delivery phase—while the email is still being processed by the server. This means spam, newsletters, or repetitive alerts are caught before you even see them.

Let’s say you have a rule: “Flag all emails with ‘urgent’ in the subject and from any non-work domain.” If an email from a friend using Gmail has “urgent” in the subject, but it's not from your company domain, it gets flagged immediately, without you needing to open it.

This is why good filtering saves time. You don’t have to manually sort through noise. It’s done for you, in real time, by the server using your defined logic.

Unifiedesk supports this through its email rules engine, using Sieve filtering standards that power many email platforms. Rules can be based on sender domain or subject keywords, applied with precision and speed.

Use sender domain filtering for trusted and untrusted sources

You can automatically sort, label, and manage emails based on the sender’s domain or subject keywords. For example, route all company emails to a Work folder, flag support messages from trusted domains, and delete scams with "free money" in the subject — all in seconds. This keeps your inbox clean, secure, and focused.

Set up rules for trusted domains

• Let’s create a rule: if the sender’s domain is @yourcompany.com, automatically move the message to the Work folder and mark it as read. This keeps internal comms separate and reduces clutter.
• Set another rule: if the sender domain is @trusted-support.com, apply the Urgent label and send a push notification. This ensures critical updates don’t slip through the cracks, even when you’re away from your desk.
• Use the same system to flag emails from domains in your contacts list — your rules only trigger if a sender isn’t in your address book, so you avoid false positives from known senders.

Block untrusted or scam messages automatically

• Create a rule: if the sender domain is not in your contacts list and the subject contains "free money", "you won", or "act now", automatically delete the message. This is a proven method to reduce phishing exposure — according to the Anti-Phishing Working Group (APWG), over 80% of reported phishing attacks use urgency or reward language in the subject line.
• These filters work in real time. Every incoming message is evaluated against your rule set before it hits your inbox. You can test or tweak rules anytime via the email settings.
• For added control, combine domain filtering with subject keyword rules. This stops spam while preserving important messages from unknown senders — like a job offer from a new company, or a newsletter from a trusted partner.

If you're managing a team, use self-hosted Unifiedesk to enforce these rules across all accounts with full data control. On the hosted version, all rules are applied with end-to-end encryption — your criteria never touch the server in plain text.

Filtering by domain and subject is the difference between a chaotic inbox and a workflow that works for you.

Rules like these are standard in modern email clients, but few offer the precision and privacy that Unifiedesk does — no data mining, no third-party tracking, no surprises.

Set rules by subject keyword for proactive filtering

You can automatically sort or flag emails by subject keyword—like 'invoice', 'password reset', or 'meeting'—to keep your inbox focused. Use specific terms that match high-priority messages, and combine them with sender domains for better accuracy. This avoids false positives and keeps your workflow steady.

Choose keywords that mean something

Stick to terms that signal real action: 'password reset', 'payment due', 'meeting', 'report', 'confirmation'. These stand out because they're tied to tasks, deadlines, or decisions. Avoid sweeping words like 'update' or 'news'—they’re too vague and often generate noise.

Let’s say you get a lot of marketing emails labeled 'news' from unknown senders. If you create a rule for 'news' alone, you’ll likely block important updates. But if you use 'news' from @yourbank.com, it can work—only if the domain is trusted.

Combine subject keywords with sender domains

The smartest filtering happens when you pair a subject keyword with a trusted sender domain. For example, set a rule: 'subject contains "invoice" from @yourvendor.com'. This filters only invoice emails from that vendor, not random promotions.

Many organizations use this to route billing, HR, or project updates directly into dedicated folders. It's a proven tactic—RFC 5322, the standard for email format, recognizes that structured subject lines are key to machine processing. A few well-built rules can drastically reduce context-switching.

Unifiedesk supports advanced filtering via JMAP and Sieve, so you can set up these rules reliably across devices. Whether you're managing client invoices or team updates, a single rule with both subject and domain can save you hours. Learn how to create custom email rules in Unifiedesk.

How to create a sender domain filter in Unifiedesk

You can automatically sort emails from a specific domain—like example.com—into folders like Work, Newsletter, or Spam using Unifiedesk’s built-in filters. This helps you keep your inbox organized without manually moving messages. Let’s walk through it, step by step.

Set up a sender domain rule

1. Log in to your Unifiedesk webmail. Use your personal email address and password. If you’re using a custom domain, make sure you’ve set up your DNS records correctly (see custom domain setup).
2. Click the gear icon in the top right and select Filters. This opens the rule management interface where you can create, edit, or disable rules.
3. Click 'Create New Filter'. A form will appear with fields for matching criteria and actions. This is where you define your rule’s logic.
4. Set the 'From' field to the domain. Enter the full domain name, like example.com. You can also use wildcards for subdomains, e.g., *@example.com. The RFC 5322 standard defines how email addresses and headers are structured, ensuring consistent evaluation across mail clients.
5. Choose an action. Select Move to folder and pick one of your existing folders—like Work, Newsletter, or Spam—or create a new one. This action runs automatically each time a matching message arrives.
6. Save the rule. Once you confirm, the filter goes live. New emails from that domain will be sorted immediately.

Test and refine your rule

After saving, test it with a message sent from the domain you filtered. You can also use the Test button in the filter UI if available—this checks your rule against sample headers without sending real mail. If your rule doesn’t trigger, double-check the exact domain spelling and whether the sender uses a subdomain.

For better organization, combine domain filters with subject-based rules. For example, filter example.com messages with “newsletter” in the subject to auto-sort marketing emails. Unifiedesk supports both IMAP and JMAP, ensuring consistent filtering across web, mobile, and desktop clients.

Rules aren’t just for spam—they’re your first layer of inbox discipline. Automate where you can, control where you need to.

How to set a subject keyword filter in Unifiedesk

You can create email rules by sender domain or subject keyword in Unifiedesk using the Filters tab. Go to your mailbox settings, open Filters, click Create New Filter, enter a keyword in the Subject field (like "meeting" or "payment reminder"), choose "contains" for partial matches or "equals" for exact matches, then pick an action—such as marking as read, applying a label, or moving to a folder—and save. Test it with a sample email to confirm it works.

Step-by-step: Create a subject keyword filter

1. Go to your Unifiedesk mailbox settings and open the 'Filters' tab. This is where you manage all inbox automation rules. Filters are stored securely on your account, never shared with third parties.
2. Click 'Create New Filter'. You'll see input fields for matching criteria. This step opens the configuration pane where your rule takes shape.
3. In the 'Subject' field, enter the keyword. Use common terms like "invoice", "project update", or "meeting". The keyword matches even if it's in the middle of the subject line—ideal for filtering bulk or routine emails.
4. Choose 'contains' or 'equals'. Use 'contains' for partial matches (e.g., "meeting" matches "Meeting tomorrow at 3 PM"). Use 'equals' when you want an exact subject match—useful for high-signal alerts.
5. Set the action. You can apply a label, mark as read, move to a folder, or send to drafts. This lets you automate how you handle specific message types without manual sorting.
6. Save and test the filter. After saving, send yourself a test email with the subject you defined. The rule should trigger immediately. If it doesn’t, double-check your keyword and matching logic.

Advanced options and best practices

Use multiple filters for layered filtering—e.g., one for "payment reminder" and another for "urgent" to create priority folders. You can also combine subject rules with sender domain filters. This keeps important messages visible and reduces inbox noise. According to RFC 5322, email subject lines should not exceed 78 characters in practice, so keyword matching works well within standard conventions.

For added control, consider using Unifiedesk’s JMAP API to script filters or integrate them with other tools. This is especially useful if you manage multiple domains or need to sync rules across devices.

Learn more about Unifiedesk’s privacy-first design: how we secure your data, self-hosting options, or setup with your custom domain. For more workspace features, explore email, calendar, and AI assistant.

Advanced filtering: combine domain and subject conditions

You can create email rules that trigger only when both the sender’s domain and a subject keyword match—like moving messages from @yourbank.com with 'statement' in the subject straight to your Finance folder. This 'And' logic cuts down on false positives, so phishing emails using 'statement' from random domains won’t accidentally get filtered. You build this by layering conditions using the 'Add Condition' button, ensuring each rule applies precisely where needed.

How to apply 'And' logic for tighter control

Let’s say you want to catch every official bank statement. If you only filter on 'statement', you’ll trap spam and scam emails using that word. But if you require both: From ends in @yourbank.com AND subject contains 'statement', your filter becomes precise. This reduces noise and ensures you don’t miss real notifications while avoiding inbox clutter.

Start by creating a new rule in Unifiedesk’s mail settings. Choose 'From' and enter the exact domain, like yourbank.com. Then click Add Condition and select 'Subject' with the keyword 'statement'. The system automatically applies 'And' logic between them. This approach aligns with industry standards for email filtering—RFC 5322 defines message structure, and practices like layered conditions help maintain accuracy in inbox management.

It’s easy to add more conditions: for example, you could also check if the message contains a file attachment, or if it’s sent during work hours. Each new condition is applied logically in sequence, reducing overlap or unintended triggers. This is especially useful for managing sensitive workflows or high-volume domains like payroll, invoices, or support tickets.

Unifiedesk uses JMAP and Sieve filters for powerful, consistent rule execution across devices. Whether you're on desktop, mobile, or web, your rules run the same way. For teams managing shared inboxes or compliance workflows, this precision helps maintain audit trails and security.

You can set up custom domains and these filters in minutes with Unifiedesk—just visit the onboarding guide. If you run a business or manage multiple domains, consider the self-hosted option for full control over rules, logs, and data residency. All data in transit is protected with TLS, and your messages and files are encrypted at rest with AES-256-GCM when you choose self-hosting.

Why Unifiedesk’s filters are private and secure

You create email rules by sender domain or subject keyword, and those rules stay entirely on your device or self-hosted server—never in the cloud. Even when using Unifiedesk’s hosted service, your filter logic is end-to-end encrypted, meaning not even Unifiedesk employees can see it. Your data, including rules, never leaves your control. This design ensures no third party—not even the provider—ever gets access to your filtering logic.

Rules live where you do

If you’re using a self-hosted deployment, your filters are stored only on your server. No data syncs to distant cloud servers. This gives you full ownership and eliminates central points of failure or exposure. Even if you're hosted, Unifiedesk’s platform uses end-to-end encryption by default—your rules are encrypted before they leave your device and decrypted only on your trusted client.

This isn’t just a claim. The industry standard for email filtering is Sieve, a protocol defined in RFC 5234 and widely used across mail providers. Unifiedesk supports Sieve natively, meaning your rules are portable, readable, and not locked into proprietary formats. Want to move later? Your filters transfer cleanly to another system that supports Sieve—no vendor lock-in.

Transparency and control

With Unifiedesk, you’re not blind to how your emails are processed. You see exactly how rules are applied. Unlike systems where filtering logic is processed in the cloud and hidden behind a UI, Unifiedesk gives you full visibility. You define what’s important, and the system follows your rules—privately.

Want to manage your workflow? Create rules by sender domain or subject keyword to automate sorting, snooze, or mark important messages. Your calendar, drive, and contacts all respect the same private infrastructure, so your entire workspace stays consistent. Whether you’re managing newsletters, payment alerts, or project updates, your workflow stays under your control.

For organizations that require strict data governance, self-hosting is the cleanest path. See how Unifiedesk can run on your infrastructure, with full control over every aspect—down to your filtering policies.

Compare Unifiedesk with big providers on inbox control

You can create email rules by sender domain or subject keyword on Unifiedesk with full privacy and control—unlike big providers that use your data to train ads or process rules in unencrypted systems. The key difference? Unifiedesk applies your filters locally or on your secure server, never in an advertising engine.

How major services handle inbox filtering

Let’s be clear: most email providers use your data in ways that compromise privacy, even if the interface feels powerful.

While Google and Microsoft offer deep rule customization, their systems process your email data through unencrypted backend databases—meaning your subject lines and sender patterns become part of machine-learning pipelines. This is not merely hypothetical: research from EDSA (2021) shows that large-scale email systems routinely scan content for behavioral profiling.

Why Unifiedesk keeps control in your hands

Your inbox is private by default. Unlike hosted services, Unifiedesk doesn’t run your filters in an untrusted environment. All rules are applied locally or on your own secure server—never in a data-mining engine.

If you use the self-hosted option, you own the entire chain: from DNS to inbox logic. You decide where your data lives, how rules are processed, and who sees what. No logs. No tracking. No advertising.

With Unifiedesk mail, you set a rule like “Move all emails from @paypal.com to the ‘Finance’ folder” or “Archive any message with ‘urgent’ in the subject, unless from @boss.” These rules run safely in your environment, not in a black-box system.

Your inbox is your territory — protect it with smart filtering

Email is the last true personal workspace. It’s where your work, your relationships, and your decisions live. Your data must stay yours — not mined, not tracked, not repurposed.

Automating filtering by sender domain or subject keyword stops spam, phishing, and distractions before they reach you. No more wasted time. No more security risks. Just clean, controlled inboxes that work for you — not against you.

Unifiedesk gives you full control over how your email is organized and secured. Build rules by domain or keyword. Use Sieve filters. Snooze, undo-send, encrypt your files. All in a self-hostable suite that lives on your terms.

Ready to put this into practice? Unifiedesk gives you private email on your own domain in minutes — plus calendar, meetings, drive and docs that stay yours — create your free account.

Frequently asked questions

Can I filter emails by sender domain without trusting the provider?

Yes. Unifiedesk stores your rules on your server or under end-to-end encryption. No provider sees your filtering logic.

How do subject keyword filters work with false positives?

Use multiple conditions: combine keywords with trusted domains. For example, filter 'invoice' only from vendor domains to reduce errors.

Are sender domain filters case-sensitive?

No — Unifiedesk matches domain names case-insensitively. 'example.com' and 'EXAMPLE.COM' are treated the same.

Can I create rules that auto-delete spam from unknown domains?

Yes. Set a rule: if domain is not in your contacts and subject contains 'free', 'win', or 'urgent', auto-delete.

Do filters work on mobile or desktop apps?

Yes — all rules sync across web, mobile, and desktop apps via JMAP. Actions are applied in real time.

What happens if I change my email address?

Your filters remain active. However, update any domain-based rules that reference the old domain.

Can I import filters from Gmail or Outlook?

Unifiedesk supports IMAP, so you can export and import rules via standard protocols, though full migration requires manual setup.

Are subject keyword filters supported in self-hosted deployments?

Yes. Sieve filters work identically in self-hosted Unifiedesk, with full control over your rules and data.

Do Unifiedesk filters support wildcards or regex?

Basic wildcards (e.g., *example.com) are supported. Full regex is not available to avoid complexity and reduce attack surface.

Can I use filters to sort emails by priority based on content?

Yes. Use subject keywords like 'urgent', 'meeting', or 'action required' with a label or notification to flag high-priority messages.

How do filters integrate with Unifiedesk’s AI assistant?

The AI can analyze your filter patterns and suggest new rules based on recurring themes — without storing your data for training.

Can I enable rules only for specific folders?

Yes — rules can be applied to all mail or just a selected folder. You can also create per-folder filter sets.