Lob

Send physical mail programmatically with Lob. Agents verify and standardize US addresses, maintain reusable address records, create postcards, letters, and checks from HTML or templates, and audit sent mail with status and proof URLs.

7 actions Basic auth available

Lob website ↗ Platform Documentation ↗ Capability data verified 2026-07-28

A statement run is due, and the recipient list lands from the CRM

Verify US Address checks and standardizes every mailing address on the list

Agent splits the list by deliverability rating, deliverable pieces proceed, undeliverable and no_match rows are pulled aside

Create Address saves corrected addresses as reusable records for future runs

The mail owner reviews the batch summary and a rendered proof before any paper prints

Create Letter generates and sends each approved piece from the template with merge data

The operations channel gets the run report: pieces sent, proof URLs, and the rejected-address list

The rejected rows route back to the CRM for address cleanup

What This Integration Enables

Physical mail is the channel that cannot be marked as read and ignored, and Lob makes it callable: postcards, letters, and checks created from HTML or templates, delivered through the postal system with API-grade tracking. The catch that separates mail from every digital channel is finality. There is no unsend, and every piece costs real money the moment it is created. FlowRunner agents are built for exactly that shape of work: they do the verification, personalization, and logging at machine speed, and put a person in front of the moment paper gets committed. - Verify and standardize US addresses before shipping, invoicing, or mailing - Trigger printed welcome postcards and onboarding letters when customers sign up - Send statements, notices, and marketing letters from HTML, hosted PDFs, or Lob templates - Maintain a reusable address book for recipient and return addresses - Audit sent postcards, letters, and checks with status and proof URLs The [human-in-the-loop](/concepts/human-in-the-loop) gate here is not a formality. It is the difference between an automated mailroom and an automated money incinerator.

Without FlowRunner

Mail runs are a vendor project Every statement or campaign means exporting a list, emailing a print shop, and waiting days for a batch

Undeliverable mail is discovered by return Bad addresses get printed, mailed, paid for, and come back weeks later as waste

No audit trail on paper What was mailed to whom, and what it looked like, lives in an email thread with the printer if it lives anywhere

With FlowRunner

Mail is a workflow step A letter or postcard is one action call away from any trigger in the stack, at any batch size

Addresses are verified before a cent is spent Every piece checks deliverability first, and bad addresses route to cleanup instead of the mailbox

Every piece has a proof and a status Sent mail is listable with proof URLs and processing status, logged automatically

Use Case Scenarios

Statements that only mail to addresses that exist

Contacts come out of [HubSpot](/integrations/hubspot). The agent runs Verify US Address on each mailing address, keeping the deliverable ones and flagging vacant and undeliverable results back to the CRM. The statement run goes to the mail owner as a summary with a rendered proof; on approval, Create Letter sends each personalized statement from the template. Postage gets spent on mailboxes, not on address rot.

The welcome postcard that beats the onboarding email's open rate

A signup arrives via [Typeform](/integrations/typeform). The agent verifies the address, saves it with Create Address, and queues a welcome postcard from the approved template. Single transactional pieces from a template a human already approved flow straight through Create Postcard, and the signed proof URL logs to the customer's record. A physical card lands on the new customer's desk during their first week, from a flow nobody touched.

The paper audit trail, assembled nightly

Compliance wants to know what went out. Each night the agent pages through List Postcards, List Checks, and the address book via List Addresses, appending each piece's ID, recipient, status, and proof URL to [Google Sheets](/integrations/google-sheets), with a digest to [Slack](/integrations/slack). When a customer disputes ever receiving a notice, the answer is a proof image and a processing status, not a shrug.

Human-in-Loop Highlight

Create Letter is a purchase order and a publication in one API call: the moment it succeeds, a physical document is queued for print and postal delivery, the money is spent, and nothing recalls it. Scale is what turns a typo into an incident, a merge-field bug that renders "Dear {{first_name}}" or last quarter's balance does not fail one email, it prints five thousand times and lands in five thousand real mailboxes with your logo on it. So FlowRunner batch flows never go from data to paper without a person seeing paper first. The agent verifies every address, renders the piece, and posts the gate: "Statement run: 4,918 deliverable, 143 rejected addresses attached, proof URL for a sample piece here, estimated spend at current postage. Print?" The mail owner opens the proof, reads what a customer will hold in their hands, and approves. Pre-approved single-piece templates flow automatically; anything new, batched, or carrying computed dollar amounts waits. Paper does not have a rollback, so the review happens before the print, every time.

Agent processes routinely

Detects exception requiring judgment

Clear match Continues automatically

Ambiguous Routes to human via email

Human decides

Agent resumes with decision

Agent Capabilities

7 actions

Address Verification

Verify US Address Verifies and standardizes a US address, returning a deliverability rating from deliverable through undeliverable and no_match, corrected components, and DPV, vacancy, and active-status analysis flags. The preflight that runs before any piece is created.

Addresses

List Addresses Retrieves saved addresses, most recent first, with cursor pagination and a total count. The address book read behind recipient selection.
Create Address Saves a reusable address record with an adr_ ID for use as a to or from on any mail piece. The step that turns a verified address into infrastructure.

Postcards

List Postcards Retrieves created postcards with status, cursor pagination, and total count. The audit read for campaign logging.
Create Postcard Creates and sends a postcard, with to and from as saved address IDs or inline fields, and front and back from HTML, a hosted PDF or PNG, or a template ID. Returns a signed proof URL and processing status.

Letters

Create Letter Creates and sends a letter from HTML, a hosted PDF, or a template, in color or black-and-white, optionally double-sided. Returns a signed proof URL and processing status. The operation this page's human gate exists for at batch scale.

Checks

List Checks Retrieves created checks, most recent first, with cursor pagination and total count. The reconciliation read for finance flows auditing what paper payments went out.

Frequently Asked Questions

What can FlowRunner do with Lob?

FlowRunner agents can run Verify US Address, List Addresses, and Create Address in Lob, plus 4 more actions.

Does connecting Lob to FlowRunner require OAuth?

No. Lob connects to FlowRunner with basic authentication (a username and password), no OAuth flow required.

Can Lob trigger a FlowRunner workflow automatically?

Lob doesn't currently expose triggers in FlowRunner. It connects as an action step inside workflows started by another trigger.

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