Buyer guide · SimpleVerifier Team
Email verification for Postmark senders
Postmark's Servers FAQ says it requires a bounce rate below 10% and a spam complaint rate below 0.1%, and a server turns orange as it nears the limit. Verify addresses before Postmark sends to them: SimpleVerifier's API checks a sign-up address in one call, and a CSV upload checks a list. Send valid, hold risky. The first 100 checks are free; Pro is $39 a month.
The limits are quoted from Postmark's Servers FAQ. Two common sources of bounces are addresses mistyped or invented at sign-up, and old lists imported into a broadcast stream. Both can be checked before the first send.
SimpleVerifier facts: prices, packs and limits
- What it is
- Email verification with a real SMTP mailbox check: each address comes back valid, risky or invalid with a reason. Includes an email finder on Pro and up.
- Price per check
- Starter $9/mo for 2,500 ($3.60 per 1,000); Pro $39/mo, 100,000 a month at full speed ($0.39 per 1,000 when used), then slower, never cut off. Business $99/mo with 300,000 at full speed; Agency $249/mo with 750,000 at full speed.
- One-time packs
- 10,000 for $15 ($1.50 per 1,000); 25,000 for $29 ($1.16 per 1,000); 50,000 for $49 ($0.98 per 1,000); 100,000 for $79 ($0.79 per 1,000); 250,000 for $169 ($0.68 per 1,000). Credits never expire, run at standard speed, CSV verification only (no API or finder).
- Free checks
- First 100 email checks free with a Google sign-in, no card, once per account. Single checks on the free email checker need no account.
- Billing
- Monthly subscription, cancel anytime (yearly billing optional). One-time packs are listed above. Starter allowances reset monthly and do not roll over.
- Speed today
- One sending IP today, shared by every customer: about 13,000 mailbox checks a day in the standard lane. Bad syntax, dead domains and disposable addresses return at once; a list of 100,000 takes days, not hours, and each job shows its estimated finish time.
- Catch-all handling
- Catch-all (accept-all) addresses stay risky, never valid, and are graded higher, medium or lower likelihood with the reasons. Anything a mail server does not confirm is risky.
- API and MCP
- REST API on Pro, Business and Agency (Pro includes 10,000 calls a month, then $1.50 per 1,000). Remote MCP server with 6 tools for Claude, ChatGPT, Cursor and VS Code. No API on Starter.
- Integrations
- Connects to Instantly, Smartlead, HubSpot and Mailchimp by API key: verifies a campaign or list and tags each contact with its result. CSV in and out for any other tool.
- Phone
- Free phone format checks (country, type range). Live carrier and line-type lookups come with Pro + Phone at $49.99/mo (5,000 a month). It never says a number is in service.
- Privacy and GDPR
- Data processing agreement countersigned on request (/dpa). Results files deleted 7 days after a list is submitted; confirmed results cached by address for 14 days. Lists are not used for marketing, sold or shared. Verification runs on a US server. No GDPR certification is claimed.
- What it does not do
- No sending, warmup or inbox placement tests. No published accuracy benchmark against other verifiers. Catch-all domains, Yahoo and AOL cannot be confirmed, and Outlook.com and Hotmail mailboxes are not probed while Microsoft refuses checks from our server's network: all of these come back risky, never valid.
SimpleVerifier facts from our pricing page and product. Last updated .
Test it on a real address first
Type any address. It gets the same check the paid plans run: syntax, the domain’s mail servers and, where the provider allows it, a live mailbox check. Nothing is sent to the address.
Five checks a minute, no account needed. Nothing is sent to the address — we ask its mail server whether the mailbox exists, then disconnect.
Have a list? Sign in with Google and the first 100 addresses are checked free, with results to download. No card.
By continuing you agree to our Terms and Privacy Policy.
Transactional: check at sign-up
Call the API when the form is submitted. It returns valid, risky or invalid with a reason and a send decision, flags disposable addresses (9,913 domains recognised) and runs at 120 calls a minute per key. Pro includes 10,000 calls a month included, then $1.50 per 1,000. The sign-up protection recipes use a timeout so a slow mail server never blocks a real user.
Broadcast: check the list first
Export the list, upload the CSV (up to 100,000 rows per file) and send only the valid file. Risky results are catch-all domains and providers that will not confirm a mailbox; keep them out of a server that is already near the limit. Mailbox checks are paced, because mail servers slow down or block verifiers that probe too fast, and the daily check capacity is shared between customers. Addresses that need no mailbox check, such as broken syntax, dead domains and disposable addresses, come back at once. The rest run in a queue, and the job card shows an estimated finish time.
When something else is the better fix
- The server is red because of spam complaints. Verification does not reduce complaints.
- Your sign-up flow already uses double opt-in and you never import lists. Bounces should already be low.
Common questions
- What bounce rate does Postmark allow?
- Its Servers FAQ says Postmark requires a bounce rate below 10% and a spam complaint rate below 0.1%. A server shows orange as it nears the limit and red when it exceeds it.
- Should I verify transactional email addresses?
- At sign-up, yes: a mistyped address both bounces and means your user never gets the receipt or reset link. One API call at form submit catches it.
- How much does the API cost?
- API keys come with Pro ($39 a month, 10,000 calls a month included, then $1.50 per 1,000) and up. The first 100 checks are free in the dashboard.
Check addresses before Postmark sends
Pro is $39 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 included, and you can cancel any time. For smaller volumes, Starter is $9 a month for 2,500 emails a month.
The first 100 email checks are free with a Google sign-in, no card, on the same engine the paid plans use.