# MailerSend vs Zoho CPaaS (formerly ZeptoMail)

> MailerSend scores 69.5 (B) on agent readiness against Zoho CPaaS (formerly ZeptoMail)'s 61.8 (C), and leads in 3 of 7 scored categories. Zoho CPaaS (formerly ZeptoMail) leads on schema & documentation, security & auth, payments & pricing and transparency & trust. Both do email…

- Canonical: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail
- Markdown: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.md (~2,700 tokens)
- Slim: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-08

MailerSend scores 69.5 (B) on agent readiness against Zoho CPaaS (formerly ZeptoMail)'s 61.8 (C), and leads in 3 of 7 scored categories. Zoho CPaaS (formerly ZeptoMail) leads on schema & documentation, security & auth, payments & pricing and transparency & trust. Both do email send.

- MailerSend: grade B, 69.5/100, rank #156 of 722. Markdown https://www.anchorterminal.com/tools/mailersend.md · JSON https://www.anchorterminal.com/api/v1/tools/mailersend.json
- Zoho CPaaS (formerly ZeptoMail): grade C, 61.8/100, rank #356 of 722. Markdown https://www.anchorterminal.com/tools/zoho-zeptomail.md · JSON https://www.anchorterminal.com/api/v1/tools/zoho-zeptomail.json

## Which one, for what

### MailerSend (B)

Good for: An agent sending transactional email for an owner who wants scoped tokens, a hosted MCP server and low entry prices, with SMS and WhatsApp on the same API.

Ahead on:
- Reliability, 95 against 41
- Agent ergonomics, 69 against 55
- Maintenance & community, 83 against 74

Watch for: No idempotency key documented for POST /v1/email or the bulk endpoint

### Zoho CPaaS (formerly ZeptoMail) (C)

Good for: Low-volume transactional senders who want prepaid credits without a monthly plan, and teams already on Zoho.

Ahead on:
- Schema & documentation, 78 against 73
- Security & auth, 76 against 62
- Payments & pricing, 40 against 30
- Transparency & trust, 82 against 64

Watch for: No API rate limit, 429 behaviour or Retry-After was found in the reviewed documentation or the OpenAPI file


## Score by category

| Category | Weight | MailerSend | Zoho CPaaS (formerly ZeptoMail) | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 95 | 41 | MailerSend +54 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 73 | 78 | Zoho CPaaS (formerly ZeptoMail) +5 |
| Agent ergonomics | 13% (16.2 this run) | 69 | 55 | MailerSend +14 |
| Security & auth | 14% (17.5 this run) | 62 | 76 | Zoho CPaaS (formerly ZeptoMail) +14 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Zoho CPaaS (formerly ZeptoMail) +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 74 | MailerSend +9 |
| Transparency & trust | 7% (8.8 this run) | 64 | 82 | Zoho CPaaS (formerly ZeptoMail) +18 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **69.5 · B** | **61.8 · C** | |

## Facts side by side

| Fact | MailerSend | Zoho CPaaS (formerly ZeptoMail) |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | MailerSend, Inc. | Zoho Corporation |
| Hosted endpoint | `https://api.mailersend.com/v1` | `https://cpaas.zoho.com/v1.1` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Pay per use |
| Price for email send | $4 per month (plan) | not published |
| x402 | no | no |
| Licence | Proprietary service under MailerSend's terms of use. The SDKs and the CLI on GitHub are MIT | Proprietary service under the Zoho CPaaS terms of use. The Node SDK on npm is MIT |
| Tools exposed | 127 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-29 | none |
| Terms last updated | 2026-10-05 | no date given |
| Privacy policy last updated | 2026-09-17 | 2025-12-22 |
| Customer content may train models | yes | yes |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | 175 stars, 128k npm/wk, 15k PyPI/wk | 40k npm/wk |

## Verdicts

**MailerSend.** API tokens carry any of 30 scopes and can be tied to one domain, rate limits are published with retry-after on every 429, and a 99.5 per cent SLA starts on the $35 Starter plan. Sends take no idempotency key, the Free plan allows 100 API requests a day, and the terms permit changes without notice.

**Zoho CPaaS (formerly ZeptoMail).** A public OpenAPI 3.0 file covers all 42 operations, and each Agent has its own send-only key. Email costs $2.50 per 10,000 with the first credit free. No API rate limit, 429 handling, idempotency key or SLA was found in the reviewed documentation, and new accounts wait for a manual review.

## Before you call either

### MailerSend

1. Send `Authorization: Bearer <token>` to https://api.mailersend.com/v1 and ask for a token with only the scopes the task needs, such as `email_full` and `activity_read`
2. Read the message id from the `x-message-id` response header. POST /v1/email answers 202 with an empty body
3. Check for a sent message before retrying a send. No idempotency key exists, so a blind retry can deliver twice
4. On a 429 wait the seconds in `retry-after`. Call GET /v1/api-quota, which isn't counted, to see the daily quota left
5. Use POST /v1/bulk-email for batches of up to 500 emails. It isn't on the Free plan and takes 10 to 60 requests a minute by plan

### Zoho CPaaS (formerly ZeptoMail)

1. Call the base URL for the account's region (cpaas.zoho.com, .eu, .in, .com.au, .jp or .com.cn). A key from one region fails on another
2. Send with `Authorization: Zoho-enczapikey <key>`. Logs, domains, templates, agents and suppressions need a Zoho OAuth token as `Authorization: Zoho-oauthtoken <token>`
3. Post OAuth client secrets and refresh tokens in the request body, not the query string the guide shows, so they stay out of logs
4. Don't retry a timed-out send blindly. There is no idempotency key, so look the message up by `client_reference` in the email logs first
5. Count one email per recipient, including cc and bcc, and keep each address field to 500 entries and each attachment to 15 MB
6. Use a sandbox Agent for tests. It accepts up to 10,000 emails a day and sends none of them

## Questions

### Which is better for AI agents, MailerSend or Zoho CPaaS (formerly ZeptoMail)?

MailerSend scores 69.5 (B) on agent readiness against Zoho CPaaS (formerly ZeptoMail)'s 61.8 (C), and leads in 3 of 7 scored categories. Zoho CPaaS (formerly ZeptoMail) leads on schema & documentation, security & auth, payments & pricing and transparency & trust.

### Do MailerSend and Zoho CPaaS (formerly ZeptoMail) need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call MailerSend and Zoho CPaaS (formerly ZeptoMail) without installing anything?

Yes. MailerSend has a hosted endpoint at https://api.mailersend.com/v1 and Zoho CPaaS (formerly ZeptoMail) at https://cpaas.zoho.com/v1.1.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.json, and with the fewest tokens: https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "mailersend", "b": "zoho-zeptomail"}`. From a terminal: `anchor compare mailersend zoho-zeptomail`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/mailersend.json and https://www.anchorterminal.com/api/v1/tools/zoho-zeptomail.json

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