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Deliverability Monitoring

Deliverability monitoring is the daily practice of watching the metrics that decide whether your email reaches the inbox. Three signal classes matter: bounce rate, complaint rate, engagement rate. Each one feeds back into your domain reputation with mailbox providers.

What to watch​

MetricHealthyWatchWorry
Hard bounce rate< 2%2-5%> 5%
Soft bounce rate< 5%5-10%> 10%
Complaint rate< 0.1%0.1-0.3%> 0.3%
Unsubscribe rate per campaign< 0.5%0.5-2%> 2%
Open rate (engaged audience)> 25%15-25%< 15%
Click-through rate> 3%1-3%< 1%

Hit the worry band and the platform automatically rate-limits your account. Hit it repeatedly and providers (Gmail, Outlook, Yahoo) start delivering to spam regardless of content quality.

Where to look​

  • Dashboard reports at /v2/email-marketing/reports/basic for per-campaign aggregates.
  • Webhooks for the real-time event stream. Wire delivery, bounce, complaint, unsubscribe to your monitoring stack.
  • Domain-level reputation at Google Postmaster Tools, Microsoft SNDS, and similar provider tools. Mailtarget does not surface these; check directly with each provider weekly.

Decision tree​

Hard bounce spike​

Likely causes:

  1. Imported a list with stale addresses
  2. Domain misconfigured (SPF, DKIM, DMARC alignment failing)
  3. Receiving server policy change

Action: pause the campaign; cross-check the receiving domain (one specific provider?); run Database Hygiene on the source list.

Complaint rate spike​

Likely causes:

  1. Sending to a re-engagement segment that should have been suppressed
  2. Subject line misleading
  3. Unsubscribe link broken

Action: pause the campaign; audit subject and content; verify unsubscribe link; suppress complainants.

Open rate drop​

Likely causes:

  1. Domain reputation slipping
  2. Subject line not landing
  3. Send time off-window for the audience

Action: A/B test subject; review send time vs audience; check Google Postmaster Tools for reputation signals.

Click-through rate drop​

Likely causes:

  1. Tracking domain CNAME unverified or proxied (links broken)
  2. Body content not driving action
  3. Audience not the right cohort

Action: verify the tracking domain; review CTAs; refine recipient segment.

Cadence​

CadenceWhat to check
Per-campaignBounce, complaint, unsubscribe immediately after launch
DailyAggregate across all sends; spot trend changes
WeeklyDomain reputation tools (Google Postmaster, Microsoft SNDS)
MonthlyRun Database Hygiene cleansing
QuarterlyAPI key rotation, sender domain audit

When to escalate​

Open a support ticket when:

  • Hard bounce rate above 5% with no list change explanation.
  • Complaint rate above 0.3%.
  • Sudden rate limiting (429) without volume change.
  • Domain marked as spam by a major provider.

Bring: campaign IDs, recipient segment definition, bounce sample with reason codes.