MailPace vs Resend API + MCP

MailPace 54

No OpenAPI or other machine-readable contract for the HTTPS API. The MCP server's 12 tools have typed zod inputs and output schemas, but that server isn't published yet, so partial credit (8 of 25). llms.txt answers 404 on mailpace.com and docs.mailpace.com, and no Markdown copies are served (0). The reference states what each endpoint does, and the introduction says when not to use it (transactional only, no batch, no static IPs) (12 of 20). Field tables give type, examples and required or optional, with enums for status, sort and direction and the 50-recipient cap in text (9 of 15). Examples in curl and six languages and a full table of error responses with messages, though several listed messages have a broken quote ({"error:"...) and the send reference says 30 MB where the home page says 25 MB (12 of 15). Version in the path with a promise that an old version runs until a published end-of-life date, and dated changelog posts (13 of 15). Total 54.

Resend API + MCP 95

OpenAPI spec in resend/resend-openapi, updated 30 October and typed Zod schemas on every MCP tool (25). llms.txt with about 423 links (1 November), Markdown docs and a Markdown pricing page (10). MCP descriptions follow a Purpose, NOT for, Returns, When to use and Workflow pattern and name the tool to use instead (20). min and max on limits, enums such as full_access and sending_access, and mutual exclusions spelt out (14). An errors page with typed error names, and examples throughout (14). Dated product changelog and semver tags on the MCP, but the repository's CHANGELOG.md stops at 1.1.0 and the API has no version in its path (12).

MailPace 65

Email Status API documented on 22 October 2026, and the MCP server rewritten as 2.0.0 on 4 November 2026, two days before this check (30). In the 90 days from 8 August, the Q3 changelog post of 31 August, the Email Status docs of 22 October, a mailpace-rails push on 17 October and the MCP rewrite, but only one changelog post (15 of 20). A closed service with email support. Three pull requests to the MCP repository from 2025 have no reply (8 of 15). Not in the official MCP registry (search for mailpace returned nothing on 6 November). The Node library was last pushed in October 2024 and Go in January 2024, while mailpace-rails is current (7 of 15). The MCP server gained CI with tests on 4 November; the older SDKs weren't checked for CI (5 of 10). Total 65.

Resend API + MCP 93

resend-mcp 2.27.2 on 26 October, resend-node 6.35.0 on 27 October and 6.36.0, 6.36.1 and 6.37.0 on 30 October, and the Python SDK tag v2.50.1 on 29 October (30). Six MCP releases since 6 October (2.25.0 to 2.27.2) and five Node SDK releases since 16 October (20). Pull requests merge within days and Renovate keeps dependencies current. We couldn't see issue reply times from git (18). Current official SDKs (15). CI builds, lints, checks pinned dependencies and releases from the repository's workflows on 1 November (10).

MailPace 25

No x402, MPP or L402 (0). $10 a month for 10,000 emails and $1 per 1,000 after, loaded from Paddle on the pricing page and stated in the comparison pages' tables without login (20). A free plan of up to 100 emails a month is available only by emailing support, so it isn't self-serve (5 of 20). Signup, DKIM verification and payment happen in a browser (0). Total 25.

Resend API + MCP 50

No x402, MPP or L402 (0). Plan prices and overage ($0.90 down to $0.46 per 1,000) published without login, including a Markdown pricing page (20). Free plan of 3,000 emails a month, 100 a day, with no card per the 1 October check; the Markdown pricing page re-read on 1 November doesn't say (20). Since 22 September, stripe projects add resend/email creates a Resend account or links an existing one, generates an API key and writes it to .env, so an agent can get access through the operator's Stripe login. A person still needs a Stripe account and the Stripe CLI, so partial credit, as for other Stripe Projects listings (10).

MailPace 70

Graded with the hosted lines. A public Upptime status page at status.mailpace.com, driven by the mailpace/status repository, with monitors for the application, SMTP, docs, blog and landing page and GitHub issues as incident reports (20). The 90 days from 8 August hold two incidents, an application outage on 22 September 2026 that the operator put down to an upstream provider returning 5xx (issue open for two minutes), and SMTP down on 2 November 2026 for about 35 minutes, which leaves SMTP at 99.65% for the week. Minor incidents only (20). No rate limit numbers are published; the docs say limits vary by organisation age, plan and history (0). A documented 429 with its message, no Retry-After or backoff guidance, and an Idempotency-Key on sends with written retry rules (10 of 15). The terms guarantee 99% monthly availability of the API and dashboard with a 5% credit per 30 minutes (10). The API is at v1 with no beta label (10). Total 70.

Resend API + MCP 90

incident.io status page with per-component uptime and incident timelines (20). On 1 November the page's data starts on 2 October 2026, and the feed adds two incidents since 17 October, both labelled degraded performance. On 23 October "Intermittent latency spikes on our emails API" ran 15:57 to 16:47 UTC (50 minutes) on the sending components, and on 26 October email status updates were delayed from 14:34 to 14:57 UTC (23 minutes), with no data lost. Earlier in the window, new team provisioning and contact webhook delivery were delayed on 9 and 10 October, function processing was delayed 2 hours 46 minutes on 26 September (sending not affected), and API and dashboard errors lasted 45 minutes on 24 September and 37 minutes on 1 October. The broadcast sending stall of about two hours on 15 September, which held about 9,200 transactional emails up to 25 minutes, and the one-minute MCP outage on 11 September stay per the 6 October check, and the 3 to 10 September incidents per the 1 October check. Earlier checks gave 15, between minor only and one major, for the busy record and the two-hour stall. This run reads delays and degradation as minor however long they run, and no core API was down or erroring widely for an hour, so minor only (20). 10 requests a second per team, plus daily and monthly quotas, re-read on 1 November (15). 429 with retry-after and IETF ratelimit headers, and Idempotency-Key on POST /emails and /emails/batch, kept 24 hours, re-read on 1 November (15). 99.99% uptime SLA on Enterprise (10). GA (10). 20+20+15+15+10+10 = 90.

MailPace 50

Per-domain server tokens that can only send from and read status for their domain, and an organisation token that creates, renames and revokes domain tokens through the Domains API. Tokens travel in headers only. The authentication page still tells users to contact support to regenerate a leaked token (25 of 30). No read-only token. A domain token can't touch other domains, and the unpublished MCP server has an optional recipient allowlist. No approval step on the hosted API (8 of 20). Inbound mail reaches the customer's webhook as untrusted content, and Email Status returns bounce text. The MCP README warns about prompt injection and suggests the allowlist (9 of 15). The dashboard keeps sent mail for 30 days; no log of API calls was found (6 of 15). No security.txt (404 on mailpace.com and app.mailpace.com), no disclosure policy, bug bounty, SOC 2 or ISO 27001. WebAuthn-only two-factor sign-in and Ed25519-signed webhooks are documented (2 of 20). Total 50.

Resend API + MCP 69

Bearer keys with full_access or sending_access, and a sending key can be limited to one domain. The hosted MCP signs in by OAuth with no documented scope choice (25). Sending-only keys exist, but the MCP has no read-only mode, and with a full key an agent can create keys and remove domains (10). get-received-email and the new inbox thread tools hand inbound mail to the model. Since resend-mcp 2.25.0 (6 October) local file reads by send-email attachments and create-contact-import are off over HTTP unless --allowed-file-dirs is set, and the README tells stdio users to set it to stop a prompt-injected agent attaching files outside chosen folders. That's a documented mitigation for one injection path, with no guidance on treating received mail as untrusted (4). Before 2.25.0 any local file path could be attached, including over HTTP, where a remote caller could read the server's disk; the maintainers fixed it and disclosed it in the README, read as Mapbox's 5 October fix was, as part of a public programme rather than a deduction. API request logs with full request and response bodies (14). SOC 2 Type II, an annual penetration test, a responsible-disclosure page and a security.txt with Contact and Policy but no Expires field, re-read on 1 November (16). 25 + 10 + 4 + 14 + 16 = 69.

MailPace 75

Closed hosted service under terms that name OhMySMTP Ltd with its company number. The MCP server, SDKs, landing site and status page are MIT (18 of 30). The privacy policy (30 August 2026), the pricing page and the DPA agree on retention, 30 days in the dashboard and 7 more in backups, 37 days at most (25 of 30). The API reference promises an old version runs until a published end-of-life date, and the terms list dated changes. The terms also say changes apply immediately (8 of 20). Sub-processors listed with purpose and location, Freethought hosting in the EU, Hetzner backups in Germany, AppSignal in Amsterdam, Paddle in the UK and Tutanota in Germany (18 of 20). Total 69.

Resend API + MCP 83

Closed service with published terms and an MIT MCP server (20). 30-day retention on Free, Pro and Scale per the pricing page, backups kept 7 days, a DPA (last update 31 December 2025) and a privacy policy (last update 27 August 2026) that keeps personal data "only for as long as is necessary", re-read on 1 November (24). Dated changelog, no deprecation policy found (8). 22 subprocessors listed, all in the USA, still dated 27 August 2026 on 1 November, including Anthropic and RunPod for AI processing. Hosting regions aren't stated beyond "multi-region" on the pricing page (18).