Use case · SimpleVerifier Team
Email verification for SaaS signups
Verify each SaaS signup address on your server before creating the account. Block invalid addresses and disposable domains, and let risky ones through: 27.5% of business domains in our research accept any recipient, so a form that demands a confirmed mailbox turns away real customers. Use a timeout and create the account if the check is slow.
Signup verification has two jobs that pull in opposite directions: keep throwaway accounts out of your trial and free tier, and never stop a genuine buyer at the door. The status you block on decides which job wins.
What a signup form has to handle
Throwaway accounts inflate trials and abuse free tiers
Disposable inboxes let one person open account after account. 8,740 known disposable domains come back invalid with the reason Disposable address. Check a domain by hand with the disposable email checker.
Blocking 'risky' blocks your best leads
In our Email List Health Report 2026, 46.7% of Google Workspace domains and 23.2% of Microsoft 365 domains were catch-all. If your buyers are startups on Google Workspace, nearly half their company domains cannot be confirmed over SMTP. A form that only accepts valid would reject them.
Bounced onboarding mail drags down product mail
Welcome, confirmation and password-reset emails usually share a sending domain with the rest of your product email. Bounces from junk signups count against that domain, which affects the mail paying users rely on.
Plus-addresses and dots create repeat trials
Gmail delivers jane+2@ and j.ane@ to the same inbox as jane@. These are real, deliverable addresses, so verification passes them. Limiting repeat trials is a normalisation rule in your own code; see plus addressing and trial abuse.
Where verification sits in the signup flow
Call the API from your server on submit
Send the address to the verification API from your backend, never from the browser, so your API key stays private. Node.js and Python clients are on the SDKs page.
Branch on status and reason
Invalid with Disposable address: ask for a work or personal address. Invalid otherwise: ask the user to check for typos. Risky or valid: create the account and send the confirmation email as normal.
Set a timeout and fail open
A live mailbox check waits on someone else's mail server, and some are slow. Give the call a budget that suits your form; if it runs out, create the account and verify in the background.
Keep the result on the user record
Store status and reason. Support can see why a confirmation email never arrived, and lifecycle email can skip addresses that later fail.
Re-verify dormant trials before winback
Export inactive trial users and verify the CSV before a reactivation campaign. Addresses that were fine at signup may have closed since.
What to do with each result at signup
| Result | What to do | Why |
|---|---|---|
| valid | Create the account | Confirmed mailbox. |
| risky · Accepts all addresses | Create the account | Catch-all business domain. Your confirmation email is the real test. |
| risky · Role-based address | Create the account | Teams often sign up with admin@ or dev@. Consider asking for a named address before adding seats. |
| risky · Server would not confirm / Mailbox check unavailable | Create the account, re-check later | Temporary. Do not punish the user for their mail server's mood. |
| invalid · Disposable address | Block with a clear message | Throwaway inbox. |
| invalid · Invalid format / No mail server / Mailbox not found | Ask the user to retype | Almost always a typo. They are still on the page and can fix it. |
One call from your backend at signup
curl "https://simpleverifier.com/api/v1/verify?email=jane@company.com" \
-H "Authorization: Bearer $SIMPLEVERIFIER_KEY"
{
"email": "jane@company.com",
"status": "valid",
"reason": "Mailbox exists",
"mailbox_checked": true
}Full request and response details are in the API reference.
Common questions
- Should I block risky emails at signup?
- No. Risky mostly means a catch-all business domain whose server accepts every recipient, and those are some of your most valuable signups. Block invalid and disposable results; let your confirmation email test the rest.
- Is a regex enough to validate signup emails?
- A regex catches broken syntax only. It cannot tell whether the domain has a mail server, whether it is a throwaway provider, or whether the mailbox exists. Use it as a first filter in the browser and verify on the server.
- Will a live mailbox check slow down my signup form?
- It can, because it waits on the recipient's mail server. Set a timeout that suits your form and create the account if the check has not finished, then verify in the background.
- Are API calls charged per request?
- No. API access is included in every plan and there are no per-call credits. Pro is $29.99 a month.
Get an API key
Pro is $29.99 a month with no cap on verifications: CSV uploads, the API, the Google Sheets add-on and the email finder are all included. Cancel any time.
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