New throwaway email services keep appearing. Your block list should keep up.
The free Signup Guard plugin blocks 8,201 known throwaway domains. That list only changes when the plugin updates. Pro checks every new sign-up and comment against a live list of more than 160,000 domains, refreshed every day, and refuses email domains that do not exist.
$29 a year, one site. Cancel whenever you like.
What the bundled list misses
A fake account needs an inbox for about a minute. New throwaway services appear constantly, and each new domain works until a list catches it. A list frozen inside a plugin catches it months later. By then the fake accounts, the spam comments and the free trial abuse are already on your site.
A live list, nearly 20 times larger
More than 160,000 throwaway domains, merged from two open source lists and refreshed daily. New services are caught the day they are listed, not when the next plugin update ships.
Domains that do not exist
An address at a domain that does not exist can never receive mail. Pro refuses it at the form, with a message that asks the person to check for a typo, so real people can fix it and bots cannot get through.
No delay for real people
Each domain is checked once and the answer is saved on your site for 12 hours. Gmail, Outlook, iCloud and the other big providers are never sent to us at all. Most sign-ups add no wait.
Free and Pro, side by side
Pro does not replace the free plugin. It adds a second check after the free one.
| Free plugin | With Pro | |
|---|---|---|
| Throwaway domains | 8,201, bundled | 160,000+, live |
| List updates | When the plugin updates | Every day |
| Domains that do not exist | Not checked | Refused, with a typo message |
| Your own block and allow lists | Yes | Yes, and the allow list still wins |
| Dashboard with refusal counts | Yes | Yes, plus live check counts |
| Registration and comments | Yes | Yes |
If our service is ever slow or unreachable, the sign-up goes ahead on the free plugin’s check. Nobody is turned away because of us.
Installing it
Questions
Why is this not part of the free plugin on WordPress.org?
WordPress.org requires hosted plugins to be fully functional, with nothing locked behind a licence. So the free plugin is complete on its own, and the live check lives in a separate add-on that you install from here.
Does the free plugin stop working without Pro?
No. It keeps blocking its bundled list, your own block list, and it keeps its dashboard. Pro adds the live check on top.
What happens if I stop paying?
Nothing breaks and nobody is locked out. The live check switches off and the free plugin’s bundled list keeps protecting your forms, the same as before you bought.
What does the plugin send to your service?
For each sign-up or comment that the free plugin lets through, the email address goes over HTTPS to the check, with your site’s key. Nothing is stored against the address. Your site only keeps the verdict for the domain, for 12 hours. Addresses at the big providers such as Gmail, Outlook and iCloud are never sent.
Can it turn away a real person?
It only refuses two things: a domain on the throwaway list, or a domain that does not exist at all. If someone real uses a forwarding or privacy service that is listed, add their domain to the Never block list. That list wins over everything, including Pro.
Does it cover WooCommerce or membership sign-up forms?
It checks the standard WordPress registration form and the standard comment form. WooCommerce checkout and My Account sign-ups are covered by our separate plugin, Stackedboost Email Guard, so the two never show a customer the same error twice. Membership plugins with their own sign-up form are not checked.
How many sites does one licence cover?
One. To move it to a new site, open the customer portal link in your receipt email, remove the old site’s activation, then paste the key on the new site.
Close the gap the bundled list leaves open
One site, a live list of 160,000+ throwaway domains, and a year of updates.
Get Signup Guard Pro, $29