Email Deliverability Agent with Claude Code
Nobody reads this agent's output most days, which is rather the point: it marks a bounced contact and moves on. Getting it wrong surfaces weeks later in a rep's pipeline, so the run has to check the Mailgun history, find exactly one HubSpot contact, and change only the fields your rules name. Claude Code's habit of reading everything before acting fits a job where the write is small and the check is not.
Watch it work before it's live
Run a staged conversation — no account needed. The agent handles it for real while a simulated world answers its tool calls; nothing touches real accounts, and nothing is actually sent.
Maartje de Vries
550 5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient's email address for typos. First permanent failure for this address, sent by the July invoice reminder campaign. The contact opened eleven emails before this and last clicked on 14 June.
Set up in minutes
Using this template drops you into a guided setup. It asks exactly this, nothing else:
Connect Mailgun
One sign-in. The agent acts through your account, scoped to what this template uses.
Connect HubSpot
One sign-in. The agent acts through your account, scoped to what this template uses.
Connect Slack
One sign-in. The agent acts through your account, scoped to what this template uses.
List hygiene rules
What a hard bounced address should become in HubSpot: which field to set, to which value, and where the bounce details get written. The agent only ever makes the changes this names.
Alert criteria
Which bounces are worth interrupting someone for, for example a paying customer domain, a VIP account, or more than five bounces on one domain in a day. Everything else stays silent.
Runs on Claude Code
Preselected for this page — connect your Claude Code account during setup, or switch to NoClick's built-in models with one click.
Watch it handle a test run
A staged conversation against a simulated world — then it’s live.
Why Claude Code for this agent
Checks before it writes
Bounce record, event history, then a contact search, and only then a field update. The order is the safety property here.
Handles the ambiguous match
Zero contacts or two contacts means change nothing and report it. Applying an exception rule consistently is what keeps a CRM clean.
Before you fork
How many runs will this be?
One per hard bounce, so it tracks list health rather than send volume, and a healthy list is a few hundred runs on a send day. Each run is short: two Mailgun reads, one HubSpot search and usually a single field update. A freshly purchased list will fire far more, which is itself information worth having.
Run it with a different agent
Put Email Deliverability Agent to work on Claude Code
Free to start. Guided setup, a test run against staged conversations, and it's live.