Smart. Focused. Email.
Fast, cross-platform email designed to filter out the noise - so you can focus on what's important.
Definition
💡 An email filter is a rule, yours or your provider's, that automatically sorts, labels, forwards, or hides incoming mail based on specific criteria like sender, subject line, or keywords. It's the logic behind why some emails skip your inbox entirely, and others get flagged before you even open them. Every email filter runs on the same basic structure: a condition (what to look for) and an action (what to do about it). Everything else, spam filters, auto-sorting, smart inboxes, is really just a specific application of that same idea.
What a filter decides for you
Thirty-plus emails a day doesn't sound like much until half of them are things you don't need to see the second they arrive. A filter is what decides that for you before you ever open your inbox.
A spam filter, for example, is really just one flavor of email filter, tuned specifically to catch junk and phishing attempts. A general filter can do a lot more than that. Route invoices to accounting. Keep newsletters out of your primary view. Flag anything from your biggest client so it never gets buried. Spam filtering is the narrow, automatic case. Filtering broadly is the tool, and you're the one deciding what it does.
Filters are also the simplest building block of email automation: a filter watches for a trigger and takes one action, while automation chains several filters and triggers together into a bigger workflow. Think of a filter as one gear. Automation is the whole machine.
The criteria filters run on
Every filter you'll ever build is some combination of these conditions:
Sender or recipient. The most common one. Everything from a specific address, or everything sent to an alias you use for a specific purpose.
Subject line or body keywords. Catch anything containing "invoice," "urgent," or a project name, regardless of who sent it.
Size or attachments. Useful for catching large files that would otherwise clog a mobile inbox.
Date or age. Less common, but some providers let you build rules around how old a message is.
Once a condition matches, you pick the action: label it, archive it, forward it, delete it, star it, or skip the inbox entirely. Some providers, Gmail's own filter documentation among them, let you combine several actions on one filter, so a single rule can label, archive, and forward all at once.
One detail worth knowing: filters set at the provider level (Gmail, Outlook) are server-side. They apply no matter which app or device you check mail from. A rule you build inside a single desktop client, by contrast, usually only fires on that one device. If a filter isn't working on your phone the way it does on your laptop, that's usually why.
Providers also increasingly do a version of this automatically. Auto-sorting and labels are both filter logic running in the background without you writing a single rule yourself.
Where to build one
The exact click path differs by provider, and honestly, once you've built one filter, the rest follow the same pattern: pick a condition, pick an action, save it. Gmail, Outlook, and Spark all support this, with the how-to steps for each already covered in detail over on email automation, since a single filter and a multi-step automation are built in the same settings menu.
The short version: Gmail and Outlook both let you build filters from their web settings, so they run server-side and follow you across devices. Spark doesn't have its own filter builder. It respects whatever filters you've already set up at the account level, and layers its own automatic sorting (Smart Inbox) on top.
Filter questions people run into
What's the real difference between an email filter and a spam filter?
A spam filter is a specific, automatic filter built to catch junk and phishing. A general filter is the broader tool, and you decide what it watches for and what it does.
Why didn't my filter apply to emails I already received?
Most filters only apply going forward by default. Gmail and similar providers usually give you a checkbox to apply the rule retroactively to matching messages already in your inbox. Easy to miss.
Do filters work the same across my phone, laptop, and web browser?
If the filter is set at the provider level (through Gmail or Outlook's own settings), yes, it applies everywhere. If it's built inside one specific desktop app, it usually won't.
Can Spark create its own filters?
Not directly. Spark doesn't sort emails through custom filters. Instead, its Smart Inbox automatically categorizes them into groups like People, Notifications, Newsletters, Invitations, and Invitation Responses. To control emails from a sender you don't already know, you can use Gatekeeper to accept or block new senders.