Can Resend, Postmark, or SendGrid receive email?

Not as an inbox. They are transactional sending APIs; some offer an inbound parse webhook that POSTs you raw message contents, but storage, threading, search, and any human-readable interface are yours to build. There is no mailbox behind the sending address.

What email API can both send and receive on my own domain?

Mektup - it sends transactional email through a REST API and every address is also a real IMAP/SMTP mailbox that receives replies, readable in webmail or Outlook and accessible to code and AI agents via API, MCP, and webhooks. It is fully managed; nothing to host.

Do I need Google Workspace plus a sending API to get both directions?

That is the common two-service workaround, but it means two bills and two configurations per domain, with sent mail and replies living in separate systems. A platform that does both directions on the same address avoids the split entirely.

Why Your Email API Can't Receive Email - and What to Use Instead

The half most email APIs skip

Transactional email APIs - Resend, Postmark, SendGrid, Mailgun, SES - are sending pipes. They authenticate your domain for outbound (SPF/DKIM), hand you a clean POST to fire messages, and stop there. There is no mailbox behind receipts@yourapp.com. It's an address that can speak but cannot listen.

That's why so many products send from no-reply@ - not because they don't want replies, but because their infrastructure literally has nowhere to put one.

What actually happens to replies

No inbound setup at all: the reply bounces, or silently vanishes. The customer thinks they answered you; nobody ever sees it.
An "inbound parse" webhook: some sending APIs can accept mail on a route and POST you the parsed contents. But a webhook is not an inbox - you now own storage, threading, search, attachments, spam filtering, and building a UI so a human can actually read the conversation. You've been handed a firehose and told to build email.
A separate mailbox provider: Google Workspace or a webhotel for the inbox, the API for sending - two services, two bills, two configurations per domain, and the sent mail and its replies live in different systems with no shared thread.

The test to run before picking an email provider

Ask one question: "If a customer replies to the email my app just sent, can a person on my team read it and answer - without me building anything?" If the answer is no, you have half an email stack.

What to use instead: infrastructure that does both directions

Mektup does both halves of email in one place, on domains you own. Send transactional email - verification codes, receipts, notifications - through a simple REST API, and the same address is a real IMAP/SMTP mailbox: replies land in it, threaded, readable in webmail or Outlook, searchable, with attachments. Nothing to host; Mektup runs the MX, IMAP, SMTP, and DKIM signing.

# the send looks like any transactional API...
curl -X POST https://api.usemektup.com/v1/emails \
  -H "Authorization: Bearer mek_live_..." \
  -H "Content-Type: application/json" \
  -d '{"from":"receipts@yourapp.com","to":"customer@gmail.com",
       "subject":"Your receipt","text":"Thanks for your order!"}'

# ...but receipts@yourapp.com is a real inbox.
# The reply lands there - readable by your team in webmail/Outlook,
# and by your code or AI agent via GET /v1/messages or a webhook.

Delivery status comes from the recipient server's actual SMTP response (Mektup runs its own outbound MTA, no relayhost) - so "sent / deferred / bounced" reflects what really happened, not a tracking pixel.

Where this matters most

Support and sales: the receipt's reply IS the support ticket or the buying question. Catch it.
AI agents: an agent that emails people needs to read the answers - see giving an AI agent its own inbox.
Multi-domain products and agencies: one account and API covers sending + receiving on every domain you run, instead of two services per domain.

Detailed comparison: Mektup vs Resend, or start with the transactional email guide.

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Why your email API can't receive email - and what to use instead