MailTester Email Verification
REMOTE · APP.MAILTESTER.COM
Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key.
Available components
Last scanned (5 hours ago)
Scores higher than 60% of remote servers
Reachable. Last reached 5 Nov 2026.
Category CRM and Sales
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 Security57
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- Authorisation not fully verified: no authorisation is required to call this server, and 9 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe. See how to fix → View diagnostics → Unverified
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- HSTS check failed: the Strict-Transport-Security header is absent. See how to fix → View diagnostics → Fail
- 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 (good).Pass
- Tool/resource definitions use about 675 tokens (~75/item across 9 items; 9 tools + 0 resources), lean.Pass
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management87
- Stability observed for 26 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage97
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 92% of tool parameters carry a description.Partial
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 9 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 10 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities20
- Spec-recency check failed: implements MCP spec 2024-11-05; the latest is 2026-07-28. See how to fix → Fail
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.
- 5 Nov 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 83 to 87. That category is still filling its 30-day observation window: 25 days of observed history at the previous scan, 26 at this one. The score rises as the window fills, whether or not the server changes.
- 3 Nov 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 77 to 80. That category is still filling its 30-day observation window: 23 days of observed history at the previous scan, 24 at this one. The score rises as the window fills, whether or not the server changes.
- 1 Nov 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 70 to 73. That category is still filling its 30-day observation window: 21 days of observed history at the previous scan, 22 at this one. The score rises as the window fills, whether or not the server changes.
- 30 Oct 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 63 to 67. That category is still filling its 30-day observation window: 19 days of observed history at the previous scan, 20 at this one. The score rises as the window fills, whether or not the server changes.
- 28 Oct 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 57 to 60. That category is still filling its 30-day observation window: 17 days of observed history at the previous scan, 18 at this one. The score rises as the window fills, whether or not the server changes.
- 26 Oct 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 50 to 53. That category is still filling its 30-day observation window: 15 days of observed history at the previous scan, 16 at this one. The score rises as the window fills, whether or not the server changes.
- 24 Oct 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.
- 21 Oct 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.
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 5 Nov 2026 · Probed https://app.mailtester.com/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=mailtester.com | CN=WE1,O=Google Trust Services,C=US | 15 Oct 2026 | 13 Jan 2027 | ECDSA 256 | ECDSA-SHA256 | 8059f14e917f4f8113759219d612fbfc |
| SANs: mailtester.com, *.mailtester.com | ||||||
| CN=WE1,O=Google Trust Services,C=US (CA) | CN=GTS Root R4,O=Google Trust Services LLC,C=US | 13 Dec 2023 | 20 Feb 2029 | ECDSA 256 | ECDSA-SHA384 | 7ff31977972c224a76155d13b6d685e3 |
| CN=GTS Root R4,O=Google Trust Services LLC,C=US (CA) | CN=GlobalSign Root CA,OU=Root CA,O=GlobalSign nv-sa,C=BE | 15 Nov 2023 | 28 Jan 2028 | ECDSA 384 | SHA256-RSA | 7fe530bf331343bedd821610493d8a1b |
Background: What to check on a remote MCP endpoint →
DNSSEC insecure
Validation of app.mailtester.com. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| com. | present | 19718 | 13 | Verified |
| mailtester.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 |
|---|---|
| x-content-type-options | nosniff |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://app.mailtester.com/mcp | Verified | 200 | |
| http (plaintext) | http://app.mailtester.com/mcp | HTTPS enforced | 301 | https://app.mailtester.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 →
estimate_cost ~116
Estimate the credit cost of a verification before running it, and whether the user can afford it. Provide either a count of emails, a list_id to re-verify, or an operation ('single'/'finder'). Always quote this before proposing anything billable.
| Name | Type | Req | Description |
|---|---|---|---|
| emails | integer | – | Number of emails to verify (1 credit each). |
| list_id | integer | – | Estimate re-verifying an existing list by its id. |
| operation | string | – | Operation type: bulk/single (1 credit) or finder (3 credits). |
No output schema declared.
No examples provided.
explain_result ~112
Explain what a verification status or reason means in plain English, with a send recommendation. Covers valid, invalid, catch-all/accept-all, unknown, greylisted, disposable, role, free, spam-trap, abuse, do-not-mail, no-mx, disabled, and network. Use when a user asks what a result means.
| Name | Type | Req | Description |
|---|---|---|---|
| term | string | yes | The status/reason to explain, e.g. 'catch-all', 'GREYLISTED', 'unknown', 'role'. Case-insensitive. |
No output schema declared.
No examples provided.
get_api_key ~106
Get your own free API key for this server (no account needed; 25 email verifications per day). Optional: the verification tools already work without a key on a shared trial. Returns the key once — reconnect with 'Authorization: Bearer <api_key>' for your own quota and the list tools.
| Name | Type | Req | Description |
|---|---|---|---|
| contact | string | – | Optional operator email or URL. |
| name | string | – | Your agent's name. |
| purpose | string | – | What you verify emails for. |
No output schema declared.
No examples provided.
get_batch_status ~31
Get the progress and status of a bulk verification list/job by id.
| Name | Type | Req | Description |
|---|---|---|---|
| list_id | integer | yes | – |
No output schema declared.
No examples provided.
get_credit_balance ~23
Get the current credit balance and a short usage summary for the account.
Input schema present but exposes no named parameters.
No output schema declared.
No examples provided.
get_list ~36
Get the details of a single bulk verification list by its id.
| Name | Type | Req | Description |
|---|---|---|---|
| list_id | integer | yes | The id of the bulk verification list. |
No output schema declared.
No examples provided.
list_lists ~33
List the user's bulk verification lists/jobs, most recent first.
| Name | Type | Req | Description |
|---|---|---|---|
| limit | integer | – | Maximum number of lists to return. |
No output schema declared.
No examples provided.
verify_batch ~67
Verify a batch of email addresses (up to 25 per call with an agent key). Returns per-email verdicts and saves a list. Costs 1 credit per email.
| Name | Type | Req | Description |
|---|---|---|---|
| emails | array | yes | Email addresses to verify. |
| name | string | – | Optional label for the saved list. |
No output schema declared.
No examples provided.
verify_email ~47
Verify the deliverability of a single email address. Returns a verdict (valid, invalid, risky, unknown). Costs 1 credit.
| Name | Type | Req | Description |
|---|---|---|---|
| string | yes | The email address to verify. |
No output schema declared.
No examples provided.
How do I install the MailTester Email Verification MCP server?
MailTester Email Verification is a hosted endpoint at https://app.mailtester.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 · app.mailtester.com
claude mcp add --transport http com-mailtester-email-verification 'https://app.mailtester.com/mcp'
What is the MailTester Email Verification MCP server?
MailTester Email Verification is an MCP server listed in the public MCP registry as com.mailtester/email-verification. Verify emails (valid/invalid/risky/unknown): MX, SMTP, catch-all, disposable. Free agent key. This page covers its hosted endpoint (https://app.mailtester.com/mcp).
Is the MailTester Email Verification MCP server safe to use?
MailTester Email Verification 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 MailTester Email Verification MCP server expose?
MailTester Email Verification exposes 9 tools: get_api_key, get_credit_balance, list_lists, get_list, explain_result, and 4 more. Their descriptions and schemas cost roughly 571 tokens of context every time the server is loaded.
Does the MailTester Email Verification MCP server require authentication?
No. We connected to MailTester Email Verification without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the MailTester Email Verification MCP server still maintained?
MailTester Email Verification is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.