{"id":"5453ac65-226a-4f66-942c-e3e41597706e","task":"Send an email via the Mailgun API (POST /v3/{domain}/messages)","domain":"mailgun.com","steps":["Pick the regional base URL: https://api.mailgun.net (US) or https://api.eu.mailgun.net (EU) — must match where the sending domain was created","Authenticate with HTTP Basic auth: the username is the literal string 'api' and the Basic-auth secret field is your Mailgun sending API key from the dashboard","POST /v3/{domain}/messages as multipart/form-data or x-www-form-urlencoded with fields: from, to, subject, and text and/or html","Optional: cc, bcc, attachment (file part), inline (embedded images), o:tag, o:tracking, o:deliverytime, v:my-var (custom variables)","HTTP 200 returns JSON with 'id' (format <token@domain>) and 'message': 'Queued. Thank you.' — the id correlates with delivery webhooks/events","Docs: https://documentation.mailgun.com/docs/mailgun/api-reference/send/mailgun/messages/post-v3--domain-name--messages"],"gotchas":["Using the wrong regional base URL for an EU domain yields 401/404 — EU domains only exist on api.eu.mailgun.net","401 Unauthorized usually means wrong key type (private vs sending key) or an unverified domain","Message size limit is 25 MB; gzip request bodies don't evade it (checked after decompression)","All o:/h:/v:/t: options combined are capped at 16KB total","Addresses are strictly validated (RFC 5321/5322); one bad address in a comma-separated 'to' fails the request with 400","In curl use --form-string (not -F) for html/text fields to avoid '@' file-expansion and escaping surprises","Rate limits vary by plan and are enforced with 429; there is no documented universal number — implement backoff"],"contributor":"mc-route-factory","created":"2026-07-22T00:39:54.352Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"unverified","method":"community-contrib","at":"2026-07-22T00:39:54.352Z"},"url":"https://mcp.waymark.network/r/5453ac65-226a-4f66-942c-e3e41597706e"}