Every form submission delivered
with the receipt to prove it
Point any HTML form at Postslot by BufferSol. We filter the spam, deliver to your inbox and stamp every message with its delivery status. Free for 250 submissions a month.
Free plan, no card. Spam never counts toward your limit.
Pro is $74 a year for 10,000 submissions a month. Web3Forms Pro is $149 a year for the same 10,000 (checked 3 Nov 2026, not affiliated). See the comparison
Inbox
Contact form, northfield-dental.example
f/k3Qx9…aT7w
Anna Kowalski14:02:03
DeliveredHi, can I book a cleaning for next Tuesday?
Receipt for message from Anna Kowalski
sub_01JC8F2Q · to reception@northfield-dental.example
Delivery timeline
Received14:02:03
Posted from northfield-dental.example
Sorted14:02:04
Spam score 0.04, 0 signals
Dispatched14:02:04
Handed to the mail sender
Accepted14:02:07
Accepted by the recipient's mail server
- 250
- submissions a month on Free, spam not counted
- 90 days
- of history on the Free plan
- 0 dropped
- over the limit, submissions are held, not rejected
- 1 line
- to install: change the form action
Open the letter. Show the time.
The inbox lists every submission as a ruled row with its status in words and an icon. Spam waits in quarantine with the signals that caught it. Held submissions wait for your upgrade or the next month.
Hi, can I book a cleaning for next Tuesday?
sub_01JC8F2Q · Contact form · 5 Nov 2026 14:02:03 UTC
- name
- Anna Kowalski
- anna@example.com
- message
- Hi, can I book a cleaning for next Tuesday? Mornings are best.
Delivery timeline
Received14:02:03
Sorted14:02:04
Spam score 0.04
Dispatched14:02:04
Deferred14:02:05
Recipient server asked to retry (450)
Accepted14:02:07
Accepted by the recipient's mail server
Usage this monthNOV 2026
214 of 250 delivered, 9 spam not counted, 3 held
Sample data. Over the limit, legitimate submissions are held and shown, then released when you upgrade or the month resets.
Spam never costs you a submission
Quarantined rows list the signals that caught them, such as honeypot filled or 7 links, with a Not spam button if we got it wrong.
One line to install
Change your form's action to your endpoint. Snippets for Next.js, Astro, Vue, Svelte, Webflow, Framer and WordPress are in the docs.
<!-- Paste into any HTML form -->
<form action="https://postslot.buffersoltech.com/f/<form_key>" method="POST">
<input name="name" required>
<input name="email" type="email" required>
<textarea name="message"></textarea>
<button>Send</button>
</form>Your client says the form never works. You cannot prove otherwise.
Postslot gives every submission a receipt: received, sorted, dispatched, accepted. When a client asks, you open the letter and show the time.
“Submit button does nothing.”
A form that fails quietly leaves nothing to inspect. A receipt per submission shows what arrived and when.
“The email landed in spam, or never left.”
The receipt shows whether the recipient's mail server accepted the message or asked us to retry.
“A bot sent 400 messages overnight.”
Bots are sorted out before they count. Spam never uses up your monthly submissions.
What the receipt covers
Dispatched09:14:10
Deferred09:14:11
Recipient server asked to retry (450)
Accepted09:14:19
Accepted by the recipient's mail server
Sample data.
Prove delivery, per submission
Each submission has a timeline: received, sorted, dispatched, accepted by the recipient's mail server, with timestamps.
- Spam blocked
honeypot filled · 7 links
Spam never costs you a submission
Honeypot, signed time token, self hosted ALTCHA proof of work, rate limits, domain lock and a rules engine. Real visitors see no puzzle.
- Held over limit
214 of 250 delivered, 9 spam not counted, 3 held. Sample data.
Busy month, nothing dropped
Over the limit, legitimate submissions are held and shown in your inbox, then released when you upgrade or the month resets.
https://postslot.buffersoltech.com/f/<form_key>
One line to install, every stack
Snippets for HTML, React, Next.js, Astro, Vue, Svelte, Webflow, Framer and WordPress, with your key already filled in.
Also included
90 day history on the Free plan, CSV and JSON export on every plan, signed webhooks from Starter and 250 submissions a month for free.
Three steps from form to first stamp
Step 1: Paste your endpoint
Set the form action to your Postslot URL and keep method POST. It works on static sites and on code from AI builders.
<!-- Paste into any HTML form --> <form action="https://postslot.buffersoltech.com/f/<form_key>" method="POST"> <input name="name" required> <input name="email" type="email" required> <textarea name="message"></textarea> <button>Send</button> </form>Step 2: Press Send test
The field linter checks your markup before a visitor does, for example an input with no name attribute.
Step 3: Watch the stamp land
The receipt fills in as the message is received, sorted, dispatched and accepted. Your first stamp appears in a few seconds.
Received14:02:03
Sorted14:02:04
Dispatched14:02:04
Accepted14:02:07
A form that sends is not enough. You need to know it arrived. Postslot stamps every submission, so nothing disappears quietly.
Same endpoint idea, half the price, plus a receipt
| Feature | Postslot | Web3Forms | Formspree |
|---|---|---|---|
| Free submissions a month | 250 | 250 | 50 |
| Pro price | $74 a year | $149 a year | Professional, $30 a month |
| Submissions at that price | 10,000 a month | 10,000 a month | 2,000 a month |
| Spam counts toward quota | No | {{verify}} | {{verify}} |
| At the limit | Held, not dropped | Rejected | {{verify}} |
| Delivery log per submission | Yes | No | {{verify}} |
| Free history | 90 days | 30 days | {{verify}} |
Checked 3 Nov 2026 from public pricing pages. Not affiliated with Web3Forms or Formspree. Cells marked {{verify}} are not confirmed yet. Full Web3Forms comparison
Half the price. None of the guesswork.
Annual saves 15% to 18% on plans sold both ways. Pro monthly costs about $1.30 a month more than annual.
Free
For one site and a first form
$0free
No card, no trial clock. The Free plan is the trial.
- 250 submissions a month, spam never counts
- Unlimited forms and domains
- 1 verified recipient
- 90 day history, CSV export
- Delivery receipts for every email
Starter
For freelancers with a few client sites
$24per year
Cancel anytime. Export your data.
- 5,000 submissions a month
- 3 recipients
- 1 signed webhook endpoint
- 6 month history
- Yearly billing only
Pro
Most popularFor developers who need proof of delivery
$74per year
Cancel anytime. Export your data.
- 10,000 submissions a month
- 5 recipients, 3 seats
- 5 signed webhook endpoints
- 90 day delivery log
- 1 year history
Agency
For studios running many client sites
$199per year
Cancel anytime. Export your data.
- 20,000 submissions a month
- 10 recipients, 10 seats
- 10 signed webhook endpoints
- 1 year history
- Priority support within 24 hours
Pro: 10,000 submissions a month for $74 a year or $7.49 a month. Web3Forms (web3forms.com) Pro is $149 a year or $15 a month for the same 10,000 (checked 3 Nov 2026).
Questions, answered
Web3Forms free already works. Why switch?
It does, and moving is one action URL. Switch if you want a delivery log per submission, 90 days of history on Free instead of 30, and held submissions instead of rejected ones at the limit.
Will the emails land in spam?
We cannot promise inbox placement for any sender. The receipt shows whether the recipient's server accepted a message or deferred it, so you see problems the day they happen.
Is it safe to paste the form key in my HTML?
Yes. The key is public by design, like a form action URL. Lock it to your domain in the form's allowed domains and it only accepts submissions from there.
What counts toward my limit?
Legitimate submissions, counted once when they pass the spam check. Spam and test submissions never count, submissions held over the limit count only when released, and marking one as spam gives the unit back.
What happens when I go over the limit?
We keep accepting. Extra submissions are held in your inbox and released when you upgrade or the month resets. You get a notice at 80% and 100%.
Will my AI builder understand this?
Yes. The install guide shows what to ask Lovable, Bolt, v0 and Claude Code for, and the docs are also published as plain text at /llms.txt. AI builders often generate a handler that only logs to the console; point it at your endpoint instead.
Do real visitors get a captcha?
No puzzle. The default layers (honeypot, time token, rules and a learning filter) are invisible. You can also turn on a proof of work check per form; it runs in the browser without a puzzle and is hosted by us.
What if Postslot goes down?
A submission is saved before the visitor sees success, and delivery is retried until it finishes. If saving fails, the visitor gets a clear error to try again, never a false success. We publish uptime only once we have measured it.
Do you offer a DPA, SOC 2 or HIPAA?
A DPA is on every plan. We do not offer SOC 2, SSO or HIPAA forms.
How hard is moving from Web3Forms or Formspree?
Change one action URL and the hidden field names if you used custom ones. The compare pages list the differences.
Start on the Free plan
No card, no trial clock. Cancel anytime, export everything.