Email Deliverability Agent with Codex
Bounces arrive in bursts, a few hundred on a send day and almost none between campaigns. Each one is the same small sequence: two Mailgun lookups, a HubSpot search, one update, sometimes a Slack line. Codex is fast on bounded work like that, which is what you want when the queue is three hundred deep.
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 Codex
Preselected for this page — connect your Codex 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 Codex for this agent
Built for burst volume
A send-day spike is hundreds of identical short runs. Per-run speed is the only variable that matters at that shape.
Field updates are exact
The hygiene rules name the field and the value. Writing exactly that, with the SMTP code and provider message recorded, is precise work rather than creative work.
Before you fork
Does it need write access to HubSpot?
Yes, to update the specific fields your hygiene rules name on a contact matched by the bounced address, and nothing beyond that. No delete, merge or unsubscribe operation is wired in at all, so the worst case is a field you can set back. Keep your alert criteria wide for the first week so you can watch what it does.
Run it with a different agent
Put Email Deliverability Agent to work on Codex
Free to start. Guided setup, a test run against staged conversations, and it's live.