Claude skill
Bounce Diagnosis
What do these bounces mean, and is it the list or me?
A list problem and a sender problem look the same on a dashboard and need opposite answers: one is cleaned, the other is rested. Paste the bounces or the headers and this sorts them code by code before anything else, so nobody pauses a healthy domain over a bad list, or keeps sending from a tenant Microsoft has stopped accepting.
What it runs
- Bounce codes — Every NDR classified: bad address, policy or reputation refusal, tenant-level block, or throttling
- Microsoft headers — SCL, BCL and the verdict, for “why is Outlook junking this?”
- Full headers — Authentication results and the route the message actually took
- The domain the bounces name — Reputation signals and blocklists, checked rather than assumed
- A sample of bounced addresses — Verified again, to answer “is it the list?” with evidence
What you get back
- The split first: how many bounces are the list and how many are the sender
- Each code with its count and what it means, including where Microsoft has not documented one
- The operator rule that applies: clean the list, or stop cold sending entirely and rest, then ramp back
- One next action, and new infrastructure only when the bounces name the domain or tenant and a rest has failed
Install it
Best installed with the plugin, which also connects WarmInboxes Free MCP, the tools this skill runs. On its own it is one file that falls back to the free WarmInboxes API, so there is no key and nothing to sign up for.
/plugin marketplace add Huz-ai-fa/warminboxes-claude-skills /plugin install warminboxes@warminboxes
Or this one skill on its own:
mkdir -p ~/.claude/skills/bounce-diagnosis curl -sL https://raw.githubusercontent.com/Huz-ai-fa/warminboxes-claude-skills/main/bounce-diagnosis/SKILL.md -o ~/.claude/skills/bounce-diagnosis/SKILL.md
Then just ask
You do not name the skill. Its description tells Claude when it applies.
- “Here are 40 bounces from yesterday, what is going on?”
- “We are getting 550 5.7.708 from Microsoft, is the tenant dead?”
- “Is a 6% bounce rate a list problem or a domain problem?”
Every answer cites the check behind it, so anything Claude tells you can be re-run by hand. A clean result is reported clean, with nothing to buy.