Postbox Tools
Free email checks: 24 blacklists, spoofing/BEC grade, redirect tracing, email spam test, WHOIS.
Connect it
Settings → Connectors → Add custom connector
URL: https://mcp.postboxservices.com/mcpSettings → Apps & Connectors → Advanced → Developer mode
Create connector with URL: https://mcp.postboxservices.com/mcp{
"mcpServers": {
"postbox-tools": {
"url": "https://mcp.postboxservices.com/mcp"
}
}
}claude mcp add --transport http postbox-tools https://mcp.postboxservices.com/mcp{
"servers": {
"postbox-tools": {
"type": "http",
"url": "https://mcp.postboxservices.com/mcp"
}
}
}8 tools, verified live
check_blacklistread-onlyCheck a domain against domain blacklists (Spamhaus DBL, SURBL, URIBL and others), or an IP address against 24 IP blacklists including Spamhaus ZEN, Barracuda and SpamCop. Checks the exact target given: domains are not resolved to IPs. Returns per-list listing status.
check_spoofabilityread-onlyGrade how exposed a domain is to email spoofing and business email compromise, from its public DNS (SPF, DMARC policy strength, alignment, live lookalike domains). Returns an A-F grade with findings.
trace_redirectread-onlyFollow a URL server-side through every HTTP redirect hop to its real final destination - per-hop status, IP, TLS and timing, plus phishing/deliverability flags (cross-domain jumps, https downgrades, meta/JS redirects). Fetching is SSRF-hardened (private ranges blocked, HTTPS-only, per-hop validation); how it works: https://redirect.postboxservices.com/
create_mailtestCreate a disposable test address for a full email deliverability audit (score /10: SPF, DKIM, DMARC + alignment, blacklists, reverse DNS, SpamAssassin content, Gmail/Yahoo bulk-sender compliance). The USER must then send an email from the system they want to test to the returned address, after which get_mailtest_result returns the score.
get_mailtest_resultread-onlyFetch the score and breakdown of a mail test created with create_mailtest, once the user has sent their email to the disposable address.
analyze_emlread-onlyRun a deliverability/content analysis on a raw RFC 822 email (.eml source: full headers + body). IMPORTANT LIMITS: with no live SMTP session, SPF, blacklist and reverse-DNS cannot be verified from a file - for the authoritative score use create_mailtest instead.
get_domain_ageread-onlyGet a domain's registration date and age (young domains have weak sending reputation).
whois_lookupread-onlyWHOIS summary for a domain: registrar, created/updated/expires dates, nameservers, DNSSEC, status flags.
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