SignupBouncer
REMOTE · SIGNUPBOUNCER.COM
An API that checks new signups for disposable emails and repeat accounts.
Available components
Last scanned (4 hours ago)
Scores higher than 64% of remote servers
Reachable. Last reached 17 Oct 2026.
Category Security
How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →
Endpoint Security80
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- No authorisation is required to call this server. Every tool declares its destructiveHint and none is destructive, so open access doesn't expose one. See how to fix → View diagnostics → Partial
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- The HSTS (Strict-Transport-Security) header is present. View diagnostics → Pass
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability72
- AI-judged instruction clarity (excellent).Pass
- Context-footprint check failed: tool/resource definitions use about 688 tokens (~172/item across 4 items; 4 tools + 0 resources), over budget; trim descriptions and params. See how to fix → Fail
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management3
- Stability observed for 1 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage100
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 100% of tool parameters carry a description.Pass
- Structured output schemas are declared (50% of tools); any adoption earns full credit.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 5 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.Pass
Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 17 Oct 26 0
- Stability: unverified → 0.03 ▲ functional
- 16 Oct 26 73
First indexed and scored.
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 17 Oct 2026 · Probed https://signupbouncer.com/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=signupbouncer.com | CN=YE1,O=Let's Encrypt,C=US | 14 Oct 2026 | 12 Jan 2027 | ECDSA 256 | ECDSA-SHA384 | 5e577d886b954c865fafbf751b00af5c7ae |
| SANs: *.signupbouncer.com, signupbouncer.com | ||||||
| CN=YE1,O=Let's Encrypt,C=US (CA) | CN=Root YE,O=ISRG,C=US | 3 Sept 2025 | 2 Sept 2028 | ECDSA 384 | ECDSA-SHA384 | 5ddd70dd31f801c85c186a7a04b80afe |
| CN=Root YE,O=ISRG,C=US (CA) | CN=ISRG Root X2,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | ECDSA-SHA384 | 872165fc34b6e5fba8add5b3705fb53a |
| CN=ISRG Root X2,O=Internet Security Research Group,C=US (CA) | CN=ISRG Root X1,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | ECDSA 384 | SHA256-RSA | 6c8f1dc727c7117f7baf853ac980f9cd |
Background: What to check on a remote MCP endpoint →
DNSSEC insecure
Validation of signupbouncer.com. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| com. | present | 19718 | 13 | Verified |
| signupbouncer.com. | absent | Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation |
Authentication No authorisation required
The endpoint answered without asking for a token. Anyone who knows the URL can reach it.
| Result | No authorisation required |
|---|---|
| HTTP status | 200 |
| Header | Value |
|---|---|
| strict-transport-security | max-age=31536000; includeSubDomains |
| x-content-type-options | nosniff |
| referrer-policy | strict-origin |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://signupbouncer.com/mcp | Verified | 200 | |
| http (plaintext) | http://signupbouncer.com/mcp | HTTPS enforced | 308 | https://signupbouncer.com/mcp |
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
check_email Check a signup email (and IP) ~161
Checks one email address, and optionally the signup's IP address, the way signupbouncer checks a new signup. Returns the result as "verdict" (allow, challenge or block), a 0-100 score, the reasons with their reason codes, the normalised inbox (Gmail dots and +tags folded) and the IP's network. When the domain looks like a typo of a big mail provider (gmial.com), "suggestion" holds the corrected address. Looks up the domain's mail servers live. Every reason is listed, including ones only paid plans count. Nothing sent is stored.
| Name | Type | Req | Description |
|---|---|---|---|
| string | yes | The email address to check. | |
| ip | string | – | Optional IPv4 or IPv6 address the signup came from. |
| Name | Type | Req | Description |
|---|---|---|---|
| data_version | string | – | – |
| network | object|null | – | – |
| normalized | object | – | – |
| reasons | array | yes | – |
| score | number | yes | – |
| suggestion | string | – | The corrected address when the domain looks like a typo of a big mail provider. Absent otherwise. It does not change the score. |
| verdict | string | yes | – |
No examples provided.
explain_reason Explain a reason code ~87
Explains a signupbouncer reason code (for example disposable_domain, burner_mx, repeat_inbox, datacenter_ip): what it means, how many points it adds or whether it blocks alone, and the lowest plan on which it counts. Without a code, lists every code.
| Name | Type | Req | Description |
|---|---|---|---|
| code | string | – | A reason code such as disposable_domain. Omit to list all codes. |
No output schema declared.
No examples provided.
integration_guide Code to check signups in your stack ~125
Returns the steps and the copy-paste code that checks new signups with signupbouncer in one stack: supabase (a hook, no code), fetch (any TypeScript server), nextjs, express, hono, python, firebase or better-auth. Use it when the user is building or changing a signup, register or auth flow. The code reads the API key from SIGNUPBOUNCER_API_KEY. The call has a 1.5-second limit, and any failure lets the signup through.
| Name | Type | Req | Description |
|---|---|---|---|
| stack | string | yes | The user's backend or auth stack. |
| Name | Type | Req | Description |
|---|---|---|---|
| api | string | – | – |
| docs | string | yes | – |
| files | array | yes | – |
| intro | string | – | – |
| notes | array | – | – |
| rules | string | – | – |
| stack | string | yes | – |
| steps | array | yes | – |
| title | string | yes | – |
No examples provided.
lookup_burner_domain Look up a burner domain ~112
Says whether a domain is on signupbouncer's disposable (burner) email list, a known relay service or a free subdomain mail service, or a known real mailbox provider, and when our harvester observed it. Uses only the loaded lists, no DNS lookup, so a brand-new burner domain on a burner mail server is caught only by check_email. Accepts a domain or an email address.
| Name | Type | Req | Description |
|---|---|---|---|
| domain | string | yes | A domain such as mailinator.com, or an email address. |
No output schema declared.
No examples provided.
How do I install the SignupBouncer MCP server?
SignupBouncer is a hosted endpoint at https://signupbouncer.com/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
remote · signupbouncer.com
claude mcp add --transport http com-signupbouncer-checker 'https://signupbouncer.com/mcp'
What is the SignupBouncer MCP server?
SignupBouncer is an MCP server listed in the public MCP registry as com.signupbouncer/checker. An API that checks new signups for disposable emails and repeat accounts. This page covers its hosted endpoint (https://signupbouncer.com/mcp).
Is the SignupBouncer MCP server safe to use?
SignupBouncer scores 73 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the SignupBouncer MCP server expose?
SignupBouncer exposes 4 tools: check_email, explain_reason, lookup_burner_domain, integration_guide. Their descriptions and schemas cost roughly 485 tokens of context every time the server is loaded.
Does the SignupBouncer MCP server require authentication?
No. We connected to SignupBouncer without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the SignupBouncer MCP server still maintained?
SignupBouncer is still listed as active in the MCP registry. We last reached this channel on 17 October 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.