Deliverability
What determines whether your emails land in the inbox — domain authentication, warmup, sending velocity, list hygiene — and how the Cold Email Agent protects you from the common failure modes.
Deliverability is the difference between your email landing in the inbox and landing in spam (or bouncing entirely). It's driven by four things: who you are (domain authentication), how you sound (reputation built over time), how you send (velocity and targeting), and what you send (content and list hygiene). This page covers each pillar and maps them to the tools the Cold Email Agent gives you.
The four pillars
1. Domain authentication (who you are)
Three DNS records prove to inbox providers that an email claiming to be from your domain is actually from your domain:
- SPF (Sender Policy Framework) — lists the servers allowed to send for your domain.
- DKIM (DomainKeys Identified Mail) — cryptographic signature on every email, verifiable against a public key in DNS.
- DMARC (Domain-based Message Authentication, Reporting & Conformance) — tells receiving servers what to do if SPF or DKIM fail, and where to send reports.
If any of these are missing or misconfigured, providers downgrade trust. Gmail, Outlook, and most enterprise filters now require all three for any significant sending volume.
On Acquisity-purchased pre-warmed and DFY inboxes, this is automatic. See Domain provisioning.
2. Sender reputation (how you sound)
Reputation is a score every major inbox provider maintains on every sending IP + domain combination. It's driven by:
- Engagement rate — opens, replies, click-throughs. Positive signal.
- Spam reports — users clicking "report spam". Heavily negative.
- Bounce rate — hard bounces from invalid addresses. Negative.
- Age — how long the domain/IP has been sending at this volume. Positive once aged.
Reputation is slow to build and fast to burn. A single spammy campaign on a cold inbox can tank it for weeks.
3. Sending velocity (how you send)
How fast you ramp up matters. DFY inboxes go through initial warmup before they can be attached to campaigns. Once campaign sending starts, the platform ramps volume gradually day by day until the inbox reaches its full capacity of 35 campaign emails per day.
This is what warmup solves. See Warmup.
4. List hygiene and content (what you send)
- List quality — emailing purchased lists or heavily-scraped data with a high invalid rate causes bounces, which hurt reputation.
- Content red flags — all-caps subject lines, excessive links, spam-trigger words, base64-encoded images.
- Unsubscribe compliance — missing unsubscribe link or failing to honour unsubscribes triggers CAN-SPAM / GDPR violations and erodes trust.
How the Cold Email Agent protects you
Built into the product:
| Protection | Where |
|---|---|
| Pre-warmed inboxes — arrive with established reputation | Buying inboxes |
| Automatic SPF / DKIM / DMARC on Acquisity domains | Domain provisioning |
| Continuous warmup — simulated traffic maintains reputation when you're not sending at peak | Warmup |
| Sending caps per inbox — platform enforces a hard maximum of 35 campaign emails per inbox per day | Per-inbox sending limit FAQ |
| Bounce detection — bounced leads move to terminal status; agent can flag deliverability if the rate spikes | Lead lifecycle |
| Domain forwarding — 302 redirect from outreach domain to your main site raises trust signals | Domain forwarding |
| AI agent FLAG_DELIVERABILITY action — raises issues on the AI Agent tab when something looks wrong | AI Agent tab |
How to read deliverability signals
Check these regularly on every active campaign:
- Bounce rate in Analytics. Healthy cold email keeps bounces under 3%. Anything over 5% indicates list-quality or auth issues and needs intervention.
- Inbox health score in the Email Accounts table. Dropping health on an inbox is a leading indicator of reputation decay.
- AI Agent tab — deliverability-related entries list the checks or conditions the agent noticed.
- Positive Reply Rate. A sudden collapse in PRR across a campaign that was working is a sign messages are going to spam even if the sent counter looks normal.
The burnt-inbox playbook
When an inbox's reputation is genuinely burnt (high bounce rate, low engagement, spam-folder placement), recovery is slow and not guaranteed. Usually faster to rotate:
- Stop sending from the burnt inbox immediately. Pause it in the Email Accounts table.
- Review the cause. Was it a bad list, a bad campaign, or a domain-auth slip? Fix the underlying issue.
- Bring up a fresh inbox — buy a pre-warmed replacement, or buy a DFY inbox and wait for its warmup to finish before any campaign sending.
- Move campaigns to the new inbox by editing the campaign's sending account on the Options tab.
- Let the old inbox rest for weeks while warmup traffic rebuilds (or retire it entirely).
See Health & troubleshooting for details.
Sending velocity — practical numbers
Campaign sending is capped by the platform. You do not configure this yourself.
| Inbox state | Campaign sending volume |
|---|---|
| Initial warmup | No campaign sending — wait for the green flame |
| DFY ramp-up after warmup | Starts below full capacity and increases gradually each sending day |
| Full capacity | 35 campaign emails per inbox per day maximum |
Spreading volume across multiple inboxes is how you scale safely. One inbox never sends 300+ campaign emails in a day; nine inboxes at 35/day each gives you roughly the same capacity without breaking the per-inbox hard cap.
Compliance basics
Cold email is regulated differently by jurisdiction:
- United States (CAN-SPAM) — clear identification, physical address, functioning opt-out process. Add required address and opt-out wording to your copy or signature before launch.
- European Union (GDPR) — legitimate interest basis, honoured unsubscribes, documentation if challenged.
- Canada (CASL) — express or implied consent required. Stricter than US rules.
You are responsible for compliance. See the deliverability FAQ for specific questions.
Related
- Domain provisioning
- Warmup
- Health & troubleshooting
- AI Agent tab — FLAG_DELIVERABILITY action
- Deliverability FAQ