Email Deliverability Agent

A hard bounce is a permanent no, and every one you keep mailing costs sender reputation long before it costs you the list. This agent picks up each hard bounce as it fires, checks the address against its Mailgun history, marks the contact in HubSpot exactly the way your hygiene rules say, and interrupts a human only when the bounce matches your alert criteria. It never deletes a contact and never unsubscribes anyone, so the worst case is a field you can set back.

What people use it for

• Stop mailing dead addresses - The contact is marked the moment the bounce arrives, so the next campaign does not send to it again. That is the single biggest lever on inbox placement for most senders.
• Catch a blocklisting early - Several addresses at one domain failing together, or a rejection naming your sending IP, is a reputation problem rather than a bad address. It reaches Slack with the evidence instead of being filed as five list cleanups.
• Keep CRM email status honest - Sales stops chasing a contact whose mailbox no longer exists, because the field says so with the SMTP code and the date behind it. No monthly export and cleanup pass.
• Alert only on bounces that matter - A dead address at a free mail provider is routine and stays silent. A bounce at a customer domain or a VIP account pings the channel with everything needed to act.

Before you fork

What has to be connected?

A Mailgun credential with webhooks and event access for the sending domains you want watched, a HubSpot credential that can search and update contacts, and one Slack channel. During setup you write the hygiene rules, which HubSpot field gets set and to what, and the criteria that deserve a ping.

What does it cost to run?

One small run per hard bounce, so cost tracks your bounce volume rather than your send volume. A healthy 50,000 address list bouncing at 0.3 percent is around 150 runs on a send day and near zero between campaigns. A freshly bought list will fire far more, which is itself the signal.

Can it wreck my CRM?

It only sets the fields your hygiene rules name, on a contact matched exactly by the bounced address. It never deletes, merges or unsubscribes anyone, and when an address matches zero contacts or several it changes nothing and reports it. Rehearse it on the staged bounces first, then start with your alert criteria set wide and narrow them once you trust it.