AI SDR Cold Email Deliverability: Rules, Caps and Setup

AI SDR cold email deliverability depends on five things: a separate sending domain, SPF, DKIM and DMARC records, a gradual warm-up, a daily cap (BusinessMCP uses about 200 per domain) and clean, verified addresses. Automation raises sending speed, so these safeguards matter more with an AI SDR than with a human typing emails.

Why automation raises the stakes

A person sends a few dozen emails a day. Software can send thousands, and a mistake repeats at that scale. Mailbox providers watch complaint rates and bounces, and once a domain’s reputation falls, even good messages land in spam. BusinessMCP’s build guide names deliverability as the top cause of failure for AI SDR builds. Any tool you evaluate should enforce limits by default rather than rely on you to remember them.

Step 1: use a separate sending domain

Send cold outreach from a dedicated domain or subdomain that is not your primary company domain. If it is damaged, your invoices and customer emails are unaffected. BusinessMCP’s guidance recommends this, and its AI SDR product page lists a separate sending domain among its default guardrails.

Step 2: authenticate the domain

Record	What it does	Notes
SPF	Lists servers allowed to send for the domain	Often created during domain verification in the sending tool
DKIM	Signs messages cryptographically	Same, set up at verification
DMARC	Tells receivers what to do when checks fail	A TXT record you usually add yourself; start with a monitoring policy and tighten later

Google’s sender guidelines and the explanation at DMARC.org describe these requirements. For bulk senders, Gmail and Yahoo expect SPF and DKIM to pass, a published DMARC policy, easy unsubscription and low spam complaint rates. Do not send until verification shows as complete.

Step 3: warm up slowly

A new domain has no reputation. Ramp volume over days or weeks. BusinessMCP’s compliance guide gives an example ramp of roughly 10 to 15 emails a day in the first days, rising to 75 to 100 by the third week, and notes its own product ramps new domains over about ten days. Whatever the numbers, the principle is to start low and rise only while bounces and complaints stay low.

Step 4: cap volume

The BusinessMCP guide caps sending at about 200 emails per day per domain across all campaigns combined. If you need more volume, the safer answer is more warmed domains, not a higher cap on one. Also restrict sending to the recipient’s local business hours.

Key takeaway: Reputation is slow to build and fast to lose. A cap that feels too conservative is cheaper than a recovery plan for a burned domain.

Step 5: send only to verified addresses

Verify addresses before sending and hold unknown or catch-all results for review. Hard bounces should be suppressed automatically, and so should complaints and unsubscribes. BusinessMCP lists verified-address-only sending, bounce and complaint auto-suppression and one-click unsubscribe among the guardrails its AI SDR enforces by default. Whatever tool you use, confirm each exists.

Thresholds to watch

Metric	Healthy	Warning	Danger
Hard bounce rate	Under about 2%	2% to 5%	Above about 5%
Spam complaint rate	Under 0.1%	Approaching 0.3%	0.3% or higher

The bounce bands are commonly cited rules of thumb that BusinessMCP’s guide says are not official guarantees. The complaint figures follow Google’s published guidance that bulk senders should keep spam rates below 0.10 percent and avoid reaching 0.30 percent. Google Postmaster Tools shows how Gmail sees your domain.

The legal basics

Deliverability and law overlap, because the same opt-out that protects your reputation is often a legal requirement. This is general information, not legal advice, so check current rules for each market.

• United States. The FTC’s CAN-SPAM guide requires honest header and subject information, a valid physical postal address, a clear way to opt out and prompt honouring of opt-outs.
• EU and UK. B2B cold email is often run on legitimate interest, provided it is targeted and has an easy opt-out, but that is not blanket permission and national rules differ.
• Germany and Austria. BusinessMCP’s guide says German competition law generally treats email marketing without prior consent as unlawful even for B2B, and that warning letters are common. It suggests LinkedIn as the first cold channel there. See AI SDR on LinkedIn.

Checklist before the first send

1. Separate sending domain created.
2. SPF and DKIM verified; DMARC published.
3. Warm-up schedule set.
4. Daily cap configured.
5. Addresses verified; unknowns held back.
6. Unsubscribe link, sender identity and postal address in every message.
7. Approval switched on for the first batch.
8. Bounce and complaint monitoring in place.

Then follow the staged approach in how to automate SDR workflows, raise volume only after reading real results, and handle replies promptly with a clear process, as described in AI SDR reply handling.

Diagnosing a deliverability problem

Even careful senders see trouble sometimes. Signs include a sudden drop in replies with no change in the offer, rising bounce rates, and messages reported as landing in spam when you test with your own accounts. Act in a fixed order rather than guessing.

First, pause sending on the affected domain. Continuing to send while reputation is falling digs the hole deeper. Second, check authentication: confirm SPF, DKIM and DMARC still pass, since a changed DNS record or a new sending service can break them silently. Third, look at the list. A batch of old or unverified addresses is the most common cause of bounce spikes, so verify again and remove risky entries. Fourth, read the messages themselves. Link-heavy text, identical wording across thousands of recipients and aggressive subject lines all look like bulk spam.

Only after those checks should you resume, at a much lower volume, and raise it slowly while watching bounce and complaint rates. If the domain stays unhealthy, retire it and start a fresh, properly warmed one rather than sending more from a damaged address. This is another argument for using a separate sending domain: you can replace it without touching your main one.

Keep records too. A simple log of volume, bounce rate and complaint rate per domain per week lets you spot trends early, and it is the evidence you need if you ever have to explain a problem to a vendor or a customer.