How much does certified mail cost through Mailsnail?

From a prepaid balance: $8.61 for a certified letter, $11.64 with an electronic return receipt, and $14.27 with a green-card return receipt. Paying for a single letter by card: $8.83, $11.83 and $14.42. Those are one-page, black-and-white prices, all at our cost. The preview shows the exact price before anything is charged.

What's the difference between the electronic and green-card return receipt?

Both prove delivery with the recipient's signature. The electronic return receipt comes back as a PDF of the signature that get_letter links to. The green card (USPS PS Form 3811) is the physical card, signed by the recipient and mailed back to the return address on the letter.

Does Mailsnail write the legal notice for me?

No. Mailsnail prints and mails exactly what you or your agent provide. For notices with statutory requirements, such as preliminary lien notices or tenant notices, use the correct template for your state and check the rules with someone qualified.

Can I mail a PDF I already have?

Yes. Pass file_url with a link to your PDF instead of body_text, and it is mailed as is.

What if I need to stop a certified letter?

cancel_letter stops a letter before printing starts, usually possible for about a day after sending, and refunds the full price to your balance. Once printing starts it can't be cancelled.

How to send certified mail with a return receipt from an AI agent

Some mail has to go certified. Preliminary lien notices, tenant notices, demand letters and other legal notices often need proof that you mailed them, and sometimes proof they arrived. Normally that means a trip to the post office counter and a form filled out by hand. With Mailsnail connected, your AI agent can do it in one request, from Claude, ChatGPT, Cursor or any app that supports MCP.

Connect it once

Add this URL to your app as a custom connector (Claude, ChatGPT) or MCP server (Claude Code, Cursor), and sign in:

https://api.mailsnail.dev/mcp

In Claude Code that's one command:

claude mcp add -t http mailsnail https://api.mailsnail.dev/mcp

then /mcp and Authenticate. Steps for every app are at mailsnail.dev/setup.

Pick the level of proof you need

You ask for	`extra_service`	From a balance	One letter by card
Certified mail (tracking, proof of mailing)	`certified`	$8.61	$8.83
Certified + electronic return receipt (signature PDF)	`certified_return_receipt_electronic`	$11.64	$11.83
Certified + green-card return receipt (signed card mailed back)	`certified_return_receipt`	$14.27	$14.42

One page, black and white. Extra pages and color are priced at our cost, and preview_letter quotes the exact price for your letter before anything is charged.

You don't need to remember the parameter names. Say what you need in plain English and the agent picks the right one:

Send this 30-day notice to my tenant at 22 Oak Ave, Austin TX 78701 by certified mail with a return receipt. I need the green card back. Show me the proof first.

What the agent does

verify_address confirms the address is deliverable, so a notice doesn't bounce on a typo. Free.
preview_letter renders the letter, with your return address, and returns a proof PDF and the price. Nothing is charged.
You check the proof. For a legal notice, read it properly.
send_letter mails it with the certified service you asked for and returns a receipt_token.

Already have the notice as a PDF from your own template? Give the agent a link to it and it mails that file as is.

Proof of mailing and delivery

Ask the agent where the letter is, with its receipt token, and get_letter returns:

the USPS tracking number and a usps.com tracking link once the letter is mailed,
the latest USPS scan,
for an electronic return receipt, a link to the recipient's signature PDF once it's signed.

With the green card, the signed card comes back by mail to the return address on the letter.

Save the receipt token with your records. It's the key for checking that letter later.

Doing this at volume

If you send notices as part of your work, for example preliminary notices on every construction job, the same tools work inside an agent that already reads your project records. It pulls the owner, contractor and lender addresses, fills your state's template, sends each one certified, and writes the tracking numbers back to the job. See preliminary notices via MCP. For deadline-critical mail, the open-source server can also fail over between print providers with your own accounts.

What Mailsnail doesn't do

We print and mail exactly what you give us. We don't write legal content, calculate statutory deadlines, or tell you which notice your situation needs. Use the right template for your state and check the rules with someone qualified.