Is Your Agent's Sending Domain Healthy? A Monitoring Routine for AI Email
A weekly routine for watching the reputation of the domain your agents send from: delivery events, DMARC reports, Google Postmaster Tools, blocklists, and what to do when something slips.
By Toan Nhu
Domain reputation is a lagging indicator. By the time customers tell you your agent's emails are going to spam, the damage has usually been building for days. Agents make early warning more important, because a single misconfigured workflow can send a lot of mail before anyone notices. The good news is that most problems show up in data you can already collect. This is a lightweight routine you can run every week.
Signal 1: Your own delivery events
The fastest signal is the one you control. Mermail can send signed webhook events for email delivered, bounced and spam complaint, alongside received and sent. Store them per mailbox and per workflow, and chart three numbers: delivered share, bounce share and complaint count. Each endpoint's delivery history in Mermail shows recent attempts, status codes and safe failure explanations, which helps when your receiver was the thing that broke.
What you are looking for is change. A mailbox whose bounces jump from almost none to a noticeable share overnight has a new source of bad addresses. A single spam complaint on a workflow that emails existing customers deserves a look at what was sent.
Signal 2: DMARC aggregate reports
If you run agents on your own domain, your DMARC record's rua address receives daily reports from major receivers. They show every source sending mail as your domain and whether it passed authentication. Check two things: that your legitimate traffic passes with alignment, and that no unfamiliar source is sending as you. An unknown sender in the reports is either a forgotten tool or someone spoofing your domain. Both need action. Our SPF, DKIM and DMARC guide explains how to set up reporting.
Signal 3: Google Postmaster Tools
Gmail is where much of your mail will land, and Google offers free Postmaster Tools for domain owners. After verifying your domain with a DNS TXT record, you can see data such as the user-reported spam rate, authentication results and delivery errors for mail sent to Gmail users. Data only appears once you send enough daily volume to Gmail, so low-volume agents may see little. When it does appear, the spam rate is the number to watch: Google asks bulk senders to stay below 0.3 percent, and healthy agent mail should be far lower.
Microsoft offers Smart Network Data Services (SNDS) for Outlook.com reputation, but it reports by IP address and is meant for the operators of those IPs. If you send through a platform's shared IPs, as Mermail's standard plans do, SNDS is not something you would set up yourself. Dedicated IPs are an Enterprise conversation with Mermail.
Signal 4: Blocklists
Blocklists (often called blacklists) are databases that receiving servers consult to reject or filter mail. Some list IP addresses and others list domains, including domains that appear in links inside messages. Spamhaus is the most widely used; others matter less. Check your sending domain and any domains your agents link to using the list operators' own lookup tools, monthly or whenever delivery drops suddenly.
If you are listed, resist the urge to request removal immediately. Most reputable lists expect you to find and fix the cause first, whether that was a compromised form, a bad list or a runaway workflow, and they may relist a domain that keeps misbehaving. Follow the operator's published removal process, and never pay a third party that promises delisting.
A weekly routine
- Review delivered, bounced and complaint numbers per mailbox and workflow, and compare them with last week.
- Skim the DMARC report summary for failures or unknown sources.
- Check Postmaster Tools if you have enough Gmail volume to see data.
- Send one test message to inboxes you control at Gmail and Outlook and note where it lands.
- Confirm in Mermail that your custom domain still shows Sending ready and Receiving ready, since a changed DNS record can silently break either.
Monthly, add a blocklist check and a review of which workflows send the most mail and why.
When something slips: a recovery playbook
- Stop the bleeding. Pause outbound sending from the affected workflow. Replies to people who wrote in can usually continue.
- Find the cause. Look for a new address source, a prompt change that altered content, a volume spike or a loop.
- Clean up. Suppress bounced and complaining addresses and remove whatever source introduced them.
- Resume slowly. Restart with your most wanted mail, such as replies and confirmations, at low volume, and increase only while the numbers stay healthy.
Resist the temptation to abandon the domain and start a fresh one. New domains have no reputation at all, and repeating the same behavior will produce the same result. Fixing the cause is the only durable recovery.
Design for fewer surprises
The best monitoring is the kind you rarely need. Keep agent mail on a dedicated subdomain so problems stay contained, give each agent role its own mailbox so you can see which one misbehaves, cap sending in code, and suppress bounces and complaints automatically. With those in place, your weekly check becomes a two-minute confirmation that everything is still fine.
Mermail webhook payloads and verification
Signed delivery, bounce and complaint webhooks are included on Mermail's Developer plan. See Mermail pricing.
