Compare Startup Mail and Resend for custom-domain email, inbound mail, APIs, MCP, human inboxes, transactional sending, and pricing.
Startup Mail publishes this comparison. Check our product docs and the linked official sources. We say when the other product is the better fit.
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Startup Mail and Resend can both send and receive email. They organize the work in different ways.
Choose Startup Mail when a custom-domain address must serve people, teammates, products, and agents. Choose Resend when developers need a broad platform for transactional sending, inbound processing, broadcasts, and email operations.
Startup Mail is a mailbox with APIs. It stores conversations in threads and includes a human web inbox, shared and private mailbox access, forwarding, REST, webhooks, SDKs, and MCP. Its agent control plane can provision mailboxes, hold drafts, schedule sends, and enforce communication policies; administrators issue tenant- or mailbox-scoped runtime keys in the web app.
Resend is an email platform for developers. It handles transactional and marketing email, templates built with React Email, contacts, broadcasts, tracking, inbound webhooks, SMTP, SDKs, and an official MCP server.
Resend is not a send-only service. A fair comparison must account for its receiving API and stored inbound mail.
| Capability | Startup Mail | Resend |
|---|---|---|
| Custom-domain sending | Yes | Yes |
| Inbound email | Yes | Yes |
| Persistent company mailbox | Yes | Received mail is stored for the plan's retention period |
| Human working inbox | Yes | Dashboard inspection, not a shared company inbox |
| Shared and private mailboxes | Yes | No equivalent team mailbox model |
| Gmail or Outlook forwarding | Yes | Can receive forwarded mail, but not the same reply relay workflow |
| REST API | Yes | Yes |
| TypeScript SDK | Yes | Yes, plus other official SDKs |
| SMTP | No | Yes |
| Signed webhooks | Yes | Yes |
| MCP | Yes | Yes |
| Conversation workflow | Stored mailbox threads | Reply by API using the received message ID |
| Programmatic mailbox creation | Yes | Domain-level receiving rather than explicit mailboxes |
| Drafts and scheduled sends | Yes | Scheduled sends |
| React Email | No | Yes |
| Open and link tracking | No | Yes |
| Broadcasts and contacts | Prohibited | Yes |
| Dedicated IPs | No | Add-on for eligible Scale customers |
| Default retention | Until deleted; trash 30 days | 30 days on standard plans |
Resend details come from its receiving guide, MCP announcement, and pricing page. We checked them on 25 August 2026.
Older comparisons often describe Resend as a send-only API. That is no longer true.
Resend can receive mail on a managed resend.app domain or a custom domain. It emits an email.received webhook, stores the message, displays it in the dashboard, and lets an application fetch the body, headers, and attachments through its API.
If the webhook endpoint is down, Resend keeps the email and retries the event. Developers can also replay webhook events from the dashboard.
Resend's official MCP server can list and read received messages and download attachments. It can also manage sending, contacts, broadcasts, domains, and webhooks.
These features make Resend a credible option for automated inbound workflows.
Startup Mail gives each configured address a durable mailbox.
Incoming and outgoing messages stay in the same threads. A person can use the web inbox. A team can share support@company.com. A founder can keep a private address and grant specific read or send access. Gmail or Outlook forwarding sends a verified copy while the original remains in Startup Mail.
Startup Mail keeps accepted messages until a user deletes the thread or the workspace. Deleted threads stay in trash for 30 days before permanent removal. Startup Mail does not currently publish a general storage quota. See the storage and retention notes.
Resend receives mail at the domain level. Its docs state that mail to any local part on the receiving domain is accepted and can be routed from the to field. The workflow then centers on webhooks, API calls, dashboard inspection, and the application you build.
Startup Mail rejects unknown recipients because it treats mailboxes as explicit company identities. Resend's catch-all receiving model is more flexible for dynamic routing.
Choose Startup Mail when the address itself needs human ownership and mailbox permissions. Choose Resend when your code will decide what each received message becomes.
Startup Mail fits mail that people may need to read or answer.
Examples include:
hello@ shared by a small teamsupport@ used by people and an agentThe product does not require you to build a human interface around the API. It also separates workspace administration from access to private mailbox content.
Startup Mail does not support SMTP, POP, IMAP, Exchange, broadcasts, marketing lists, or drip campaigns.
Resend is stronger when the email program belongs to an engineering or growth team.
Its standard plans include REST and SMTP sending, official SDKs, scheduled email, batch sending, open and link tracking, React Email support, webhooks, and custom domains. Resend also sells a marketing product built around contacts, segments, topics, broadcasts, and automations.
Choose Resend for:
Startup Mail does not aim to match this set of sending and marketing tools.
Both products expose MCP tools, but the tools reflect different products.
Startup Mail's MCP endpoint gives an agent mailbox actions: list mailboxes, list threads, read a thread, send a message, and reply to a message. The same resource boundary and capabilities apply.
Resend's MCP server covers the wider Resend platform. An agent can work with sent and received email, contacts, broadcasts, segments, topics, domains, webhooks, and API keys.
Resend is better when an agent manages an email program. Startup Mail is better when an agent participates in a company mailbox alongside people.
In either case, an agent needs limits on recipients, sending purpose, and human approval. A technical send permission does not make every send safe.
Resend's pricing includes a Free plan with 3,000 sent and received emails per month, with a limit of 100 per day. Pro starts at $20 per month for 50,000 emails, 10 domains, and no daily limit. Free, Pro, and Scale list 30-day data retention.
Resend also has separate contact-based pricing for marketing email. A dedicated IP costs $30 per month and is available to Scale customers sending more than 3,000 emails per day.
Startup Mail costs $2 per month or $12 per year for 1,000 email events per month. An incoming delivery, each outbound recipient, and each forwarded copy count as events.
Resend includes much more email volume. Startup Mail costs less at the base tier and includes the human mailbox workflow. The products count different units, so compare the full use case.
Yes.
A startup could use Resend for password resets, receipts, product notifications, and marketing broadcasts. It could use Startup Mail for founder mail, shared support, supplier conversations, and agent-assisted replies.
This division gives Resend the high-volume delivery job and Startup Mail the human mailbox job.
Using both is less attractive when all inbound mail goes straight into your application and no person needs a company inbox. In that case, Resend may cover the whole requirement.
Choose Startup Mail if the email address belongs to a company and must work as an inbox for both people and software.
Choose Resend if email is mainly a product channel that developers manage through code, especially if you need React Email, SMTP, broadcasts, tracking, or higher sending volume.
For a shared hello@ address, Startup Mail has the clearer model. For 50,000 monthly product emails and a marketing list, Resend is the better choice.
Yes, for custom-domain company mailboxes, human and agent collaboration, forwarding, and direct transactional conversations. It is not a replacement for Resend's broadcasts, contacts, SMTP, tracking, React Email, or high-volume plans.
Yes. Resend stores inbound messages, sends webhook events, and exposes bodies and attachments through its Receiving API.
Yes. Its official MCP server covers sent and received email as well as broadcasts, contacts, domains, webhooks, and other resources.
Startup Mail, if people need a ready-made inbox and explicit mailbox access. Resend can power a support workflow, but your application must provide the working interface and assignment model.
Resend. Startup Mail prohibits newsletters, campaigns, drip sequences, and cold outreach.
Startup Mail has the lower base price for a low-volume workspace. Resend includes far more email volume and has a useful free plan. Compare your message count, forwarding copies, domains, and marketing needs.