Use case · SimpleVerifier Team
Email verification against free-trial abuse
Email verification closes the cheapest route to repeat trials: throwaway domains (9,913 known) and addresses that do not exist. It does not stop one person from using several real addresses, so add normalisation of Gmail plus-addresses and dots, and a rule tied to something other than email, such as a payment method.
Trial abuse is an economics problem. If starting another trial costs ten seconds and a disposable inbox, some people will do it again and again. Verification raises that cost a little; account rules raise it further.
Keep the goal narrow. You are not trying to identify bad users, only to make the free tier less repeatable than the paid one.
How repeat trials happen
Disposable domains
The easiest path. 9,913 domains in our list return invalid with the reason Disposable address, so a server-side check blocks the known ones. Block disposable emails at signup shows the flow.
Plus-addresses and dots
Variants of a single Gmail inbox are real, deliverable addresses. Normalise before your uniqueness check: strip the +tag and, for Gmail, the dots. See plus addressing and trial abuse.
Many free mailbox accounts
Anyone can create a new inbox at a mainstream provider. Verification passes these, as it should. Only account-level rules, such as card on file or limits per device, address this.
Over-blocking turns away buyers
A strict rule that demands a confirmed mailbox rejects company domains that accept all mail. Block invalid results and leave risky alone.
A layered defence for the free tier
Verify at signup, server-side
Send the address to the API from your backend and refuse invalid results. Fail open if the call times out; see preventing fake signups for the full flow.
Normalise before the uniqueness check
Lowercase the address, strip +tags and, for Gmail and Googlemail, remove dots. Store the normalised form next to the original and enforce one trial per normalised address.
Tie the trial to something harder to repeat
A payment method, a verified phone number or a work domain are all costlier than a new inbox. Pick what fits the friction your funnel can take.
Limit what a trial can spend
Cap the resource that costs you money, such as sends or compute, so a repeat trial is worth little even when it succeeds.
Clean the trial pool before winback
Export inactive trial users and run them through the CSV verifier before a reactivation campaign. The first 100 checks are free.
How to treat each result at trial signup
| Result | What to do | Why |
|---|---|---|
| valid | Start the trial | Mailbox confirmed. |
| risky · Accepts all addresses | Start the trial | Company catch-all domains are often your best leads. |
| risky · Role-based address | Start the trial | Teams use admin@ and dev@. Ask for a named user before seats. |
| invalid · Disposable address | Refuse, ask for another address | Throwaway inbox. |
| invalid · Mailbox not found / No mail server | Ask the user to retype | A typo or a fabricated address. |
Common questions
- Does email verification stop free-trial abuse?
- It stops the cheapest forms: disposable domains and nonexistent addresses. People using several real mailboxes or plus-address variants pass, so normalise addresses and add a rule that does not rely on email.
- Is jane+1@gmail.com a valid address?
- Yes. Gmail delivers it to jane@gmail.com, so verification marks it valid. Detect repeat trials by normalising the address in your own code.
- Should I block free email providers like Gmail?
- Only if your product is strictly for companies. Blocking them rejects individual buyers and small teams. A card on file or a usage cap is usually a better limit.
- Can I check a list of existing trial users?
- Yes. Upload a CSV and the disposable and invalid addresses are flagged, so you can see how many throwaway trials already exist. Your first 100 checks are free with a Google sign-in.
Check your trial signups
Pro is $29.99 a month and never cuts you off: the first 100,000 emails a month run at full speed, then big lists run slower. CSV uploads, the API (10,000 calls a month, then $1.50 per 1,000), the Google Sheets add-on and the email finder are all included. Cancel any time.
The first 100 checks are free with a Google sign-in and no card, once per account.