MailerSend

Send transactional emails and react to delivery events. 10 real-time email triggers let agents respond to opens, clicks, bounces, and unsubscribes. 3 actions cover every send scenario including templates and CC/BCC.

10 triggers 3 actions available

Agent sends proposal email via MailerSend template

On Email Opened First fires 90 minutes later when prospect opens the email

Sales rep receives Slack message with prospect name, deal name, and open timing

Agent monitors for bounce or non-delivery events on the same email

On Email Not Delivered fires and triggers CRM hygiene and task creation

Spam complaints routed to marketing manager to review content before template stays active

What This Integration Enables

MailerSend is both a send engine and an event stream. Agents use it to send templated and custom transactional emails, while its rich trigger set lets agents react to every meaningful email event in the recipient's journey. Bounces trigger CRM updates. Opens trigger follow-up sequences. Unsubscribes trigger compliance logging. Every email event is a workflow input.

Without FlowRunner

No open visibility Sales reps have no idea when or if proposals are being read

Bounce blindness Undeliverable addresses stay in CRM and continue to be emailed

Manual compliance logging Unsubscribes require someone to update opt-out status in every connected system

With FlowRunner

Real-time open alerts Rep notified within seconds of a prospect opening a proposal

Instant bounce processing Bad addresses flagged in CRM and removed from sequences the moment the bounce lands

60-second compliance propagation Unsubscribe logged across HubSpot, Salesforce, and Mailchimp in under 60 seconds

Use Case Scenarios

Proposal Follow-Up on Open

An agent sends a proposal email via MailerSend template. On Email Opened First fires 90 minutes later. The agent sends a Slack message to the sales rep: "[Contact Name] just opened the proposal for [Deal Name]. Good time to follow up." The rep has context, timing, and a reason to call. No manual monitoring of email open rates required.

Bounce-Driven CRM Hygiene

On Email Not Delivered fires for a contact. The agent identifies the affected contact in HubSpot by email address, marks the email as invalid, creates a task for the account owner to verify the correct address, and removes the contact from any active email sequences. Bad data gets flagged at the moment it is discovered, not during the next quarterly data cleaning exercise.

Unsubscribe Compliance Logging

On Recipient Unsubscribed fires. The agent updates the contact's communication preferences in every connected system: HubSpot, Salesforce, Mailchimp, and the internal CRM. It logs the unsubscribe event with timestamp and source in the compliance audit trail. The update propagates within 60 seconds of the opt-out, satisfying regulatory requirements without a human manually updating multiple systems.

Human-in-Loop Highlight

On Spam Complaint fires. Rather than silently suppressing the contact, the agent routes the complaint to the marketing manager via Slack: "Spam complaint received from [email] after sending [campaign name]. I've added them to the suppression list. Do you want to review the email content and remove the template from active use?" The manager reviews. If the content is problematic, they pull it. If it is a one-off complaint, they can note it and move on. Compliance with awareness, not compliance on autopilot.

Agent processes routinely

Detects exception requiring judgment

Clear match Continues automatically

Ambiguous Routes to human via Slack

Human decides

Agent resumes with decision

Agent Capabilities

3 actions

Email Sending

Send Email Sends a transactional email with custom content. Used in operational notification workflows: order confirmations, system alerts, approval requests, status updates.
Send Email with CC/BCC Sends an email with carbon copy or blind carbon copy recipients. Used when emails need to be sent to a primary contact while keeping account managers or compliance teams in the loop.
Send Email with Template Sends an email using a pre-built MailerSend template with variable substitution. Used in standardized communications: welcome emails, invoice notifications, shipping confirmations where consistent branding and structure are required.

Triggers

10 triggers

Event Triggers

On Email Sent Fires when an email successfully leaves the sending queue. Used to log delivery attempts in audit workflows and update engagement records.
On Email Delivered Fires when the receiving mail server accepts the message. Used to confirm successful delivery and timestamp the event in the CRM or ERP.
On Email Not Delivered Fires when delivery fails due to a hard bounce or server rejection. Used to trigger address verification workflows: the agent flags the contact as having a bad email, routes to the CRM for update, and notifies the account owner.
On Email Soft Bounced Fires on a temporary delivery failure: mailbox full, server temporarily unavailable. Used to trigger a retry queue or a notification that the email may need resending.
On Email Opened Fires when a recipient opens an email. Used in engagement-based workflows: when a proposal email is opened, the agent notifies the sales rep via Slack so they can follow up while the deal is top of mind.
On Email Opened First Fires only on the first open of a specific email. Used to prevent repetitive triggers in sequences where first engagement is the meaningful signal.
On Link Clicked Fires when a recipient clicks a tracked link. Used in intent-based routing: clicking a "Schedule a Demo" link triggers the agent to create a Calendly meeting link and send it to the sales rep.
On Link Clicked First Fires only on the first click of a tracked link. Used in the same intent-based workflows where first click is the conversion signal.
On Recipient Unsubscribed Fires when a recipient opts out. Used to trigger compliance workflows: the agent updates the contact's marketing preferences in HubSpot or Salesforce, logs the unsubscribe event with timestamp, and removes the contact from active sequences.
On Spam Complaint Fires when a recipient marks the email as spam. Used to trigger immediate suppression workflows and flag the contact for review.