Three kinds of third-party spam filter
The words “third-party spam filter” are used for three quite different things. Only one of them is made for a personal mailbox.
| Kind | How it works | With a personal Gmail, Outlook or Yahoo address? |
|---|---|---|
| A filter inside an email program | A program on your computer sorts the emails after it has fetched them. | Only while that program is running. Until then, every email still shows up on your phone. |
| A gateway filter for companies | All email for a company’s own address (the part after the @) passes through the filter before it is delivered. | No. It needs control over the address ending, and gmail.com, outlook.com and yahoo.com belong to the providers. |
| A filter that connects from outside | You give a service access to your mailbox. It checks new emails and moves unwanted ones into folders. | Yes. The folders are part of the mailbox, so the result shows wherever you read your email. |
Guard Mail is the third kind.
Guard Mail, scam email filter
Connects to the mailbox you already have and moves scam and phishing emails into a separate folder. Nothing is deleted.
Free to try.
How a filter from outside connects to your mailbox
A filter from outside needs your permission to read new emails and to move them. How you give it depends on the provider.
Outlook.com and Hotmail
You sign in at Microsoft and confirm the access there. Guard Mail connects to Outlook and Hotmail mailboxes this way.
Gmail
Gmail uses an app password: a separate 16-character password that you create in your Google Account for one purpose. Google requires 2-Step Verification for it. According to Google, app passwords are not available for work or school accounts, for accounts with Advanced Protection, or when 2-Step Verification is set up only with security keys. Google also removes app passwords when you change your Google password. Google: Sign in with app passwords
Yahoo Mail
Yahoo also uses app passwords. On the Yahoo Account Security page, choose Create app password, give it a name and select Generate password. Yahoo says the password stays active until you delete it. Yahoo: Generate and manage third-party app passwords
iCloud Mail
Apple calls it an app-specific password. Sign in at account.apple.com, open Sign-In and Security, then App-Specific Passwords. Two-factor authentication must be on. Apple: app-specific passwords
Good to know: an app password opens your mailbox to the service you give it to. Only give one to a service you trust. You can delete it at your provider at any time, and the access ends.
What to check before you let a filter into your mailbox
These questions are worth asking of any third-party spam filter. The right-hand column answers them for Guard Mail.
| Question | Why it matters | Guard Mail |
|---|---|---|
| What does it read, and where does that go? | A filter has to read an email to judge it. You should know what leaves your mailbox. | Sender, subject and text of each email are sent to our servers and to an AI model. Details are in the privacy policy. |
| Does it delete anything? | Every filter makes mistakes. A moved email can be found again, a deleted one cannot. | Guard Mail itself never deletes an email. Scam and phishing emails go into a folder called “Suspicious”, which is never emptied automatically. Spam goes to your provider’s own spam folder, which the provider empties after a while, usually after around 30 days. |
| Do I have to change how I read email? | A new program is one more thing to learn. | No. You keep your usual email program. |
| How do I stop it? | You should be able to end the access yourself, at your provider. | Delete the app password at your provider, or withdraw the permission in your Microsoft account. |
| What does it cost? | Look for the price per mailbox. | $6 a month or $60 a year for up to two mailboxes, each further mailbox $2.50 a month. Free to try. |
| Who runs it? | A service that reads email should say who is behind it. | The team behind email-filter.ai. See the imprint. |
Does it replace the filter of your provider?
No. The spam filter of Gmail, Outlook or Yahoo keeps working as before. A filter from outside is a second check for the emails that still reach the inbox. What each built-in filter does, and where its settings are, is described here:
Where a filter from outside fits in
Guard Mail is a third-party filter of the kind that connects from outside. In short:
- Connect the mailboxOutlook and Hotmail through a Microsoft sign-in. Gmail, Yahoo, iCloud and others through an app password. The setup explains each step. Guard Mail also works with other IMAP mailboxes.
- New emails are checkedA few minutes after an email arrives, Guard Mail checks it.
- Scam emails are movedScam and phishing emails go into a folder called “Suspicious”. Spam goes to the spam folder. Everything else stays untouched.
Guard Mail itself never deletes an email. The “Suspicious” folder is never emptied automatically. Mail providers empty their own spam folder after a while, usually after around 30 days, so look into it now and then.
If you want, newsletters, advertising and notifications are moved into their own folders as well. You can also write your own rules in plain language. You keep your usual email program.
To check an email, its sender, subject and text are sent to our servers and to an AI model. The details are in the privacy policy.
Price: $6 a month or $60 a year for up to two mailboxes. Each further mailbox costs $2.50 a month. It is free to try.
Guard Mail, scam email filter
A second check for the emails that reach your inbox.
Free to try.
Questions and answers
Is there a third-party spam filter for Gmail?
Yes. A filter that connects from outside works with a personal Gmail address. It needs an app password, which you create in your Google Account. Google requires 2-Step Verification for that.
Is there a third-party spam filter for Outlook?
Yes. For Outlook.com and Hotmail mailboxes, a filter from outside can connect through a Microsoft sign-in. Guard Mail connects this way.
Is a third-party spam filter safe?
That depends on who runs it and what it does with your email. Ask what it reads, where that goes, whether it deletes anything and how you can end the access. The table on this page goes through these questions.
Does a third-party filter switch off the built-in spam filter?
No. The filter of your provider keeps working. A filter from outside looks at the emails that arrive in your mailbox anyway.
Sources
Official pages we opened for this guide, as of November 2026.