Instantly.ai deliverability: monitoring and improving inbox placement

Instantly is the go-to cold outreach tool for teams pushing volume. The reason is obvious: warm-up, inbox rotation, unibox, bounce handling, and sequence automation in a single product, priced well for teams. Most sequencers force you to stitch these together from separate vendors. Instantly ships the whole pipeline.

The risk is that the bundled pipeline generates a single confident number — the Deliverability score in the Accounts panel — and that number is not a real placement signal. Teams scale to 300–800 sends a day on the strength of that score, then wonder why reply rates crater in week three.

What Instantly does automatically

Four automations that genuinely reduce manual work:

• Warm-up network. Connected mailboxes send and reply to each other on a ramped schedule, building positive engagement footprint. Visible under Accounts → Warmup.
• Inbox rotation. A campaign can be attached to 10, 20, or 50 mailboxes. Instantly distributes sends round-robin and respects a per-inbox daily cap.
• Bounce handling. Hard bounces are suppressed automatically across all campaigns for that workspace.
• One-click unsubscribe. Instantly injectsList-Unsubscribe and the 2024 RFC 8058 POST header. This is non-negotiable at scale and Instantly handles it by default.

Instantly's Deliverability score — what it measures

The score under Accounts → <mailbox> → Deliverability aggregates three things: warm-up email inbox rate (engagement within the Instantly network), bounce and complaint rates on outgoing mail, and auth status (SPF/DKIM/DMARC detection). It outputs a value between 0 and 100.

What it does not measure: where your real cold sends land at Gmail/Outlook/Yahoo. The warm-up network is a closed ecosystem of other Instantly customers. A mailbox can score 95 in that ecosystem and still be going straight to Gmail Spam for actual prospects — because the cold-outreach content, the cold recipient, and the unengaged domain behaviour never appear in the warm-up signal.

Weekly routine per sending inbox

1. Run an external placement test. One seed-box test per sending mailbox, per week. Gmail, Outlook, Yahoo at minimum. Attach the result to your Accounts spreadsheet so drift is visible over time.
2. Check warm-up health. Under Accounts → Warmup — inbox rate below 80% is a yellow flag, below 70% is a pause.
3. Review bounce and complaint rates for the last 7 days on each campaign. Bounce over 3%, complaint over 0.1%, pause the mailbox.
4. Check Google Postmaster Tools (for Workspace inboxes). Domain reputation should be High; Medium is borderline; Low is an emergency.
5. Audit auth and DNS. Rotations add new subdomains frequently — it is easy to forget SPF include or DKIM on a new one.

Custom tracking domain in Instantly

Under Settings → Custom Tracking Domain, point a CNAME subdomain at Instantly's tracking endpoint. The default shared tracker is fine in principle but inherits the reputation of every other workspace using it — and Instantly's customer base includes a tail of low-quality senders. Dedicated subdomain, 30 days aged, never shared across brands. Ten minutes of work that protects every link in every future campaign.

Inbox rotation configuration

Three settings inside Campaigns → <campaign> → Options that materially affect deliverability:

• Daily send limit per inbox. Gmail Workspace: cap at 40–50 cold sends/day per mailbox, not 100 or 200 that Instantly will let you set. Microsoft 365: 30–40. That is for warmed, aged, authenticated inboxes.
• Minimum delay between emails. At least 60 seconds. Bot-like patterns (every 15 seconds, precisely on the second) are a heuristic filters notice.
• Rest day logic. Enable weekend pause for B2B sends. Engagement on weekends is low; the pattern hurts.

When to pause an inbox

Pause the moment any of these show up, not a week later:

• External placement test drops from green to yellow.
• Bounce rate crosses 3% across the last 100 sends.
• Postmaster Tools shows domain reputation dropping to Medium or spam rate climbing over 0.3%.
• Warm-up inbox rate on that mailbox falls under 75%.
• Any Gmail interstitial banner ("Be careful with this message") on trial sends.

An inbox pulled early can be cooled down and re-warmed. An inbox run into the ground is dead. The asymmetry matters.

Scaling considerations

Beyond ~20 connected mailboxes, three things start mattering more than the score:

• Domain diversification. Use multiple sending domains, not 20 mailboxes on one domain. A single reputation problem drags every mailbox on it.
• Warm-up queue. Keep a rolling set of 3–5 mailboxes in warm-up so you can rotate out damaged ones without dropping campaign throughput.
• Per-segment sequences. Running the same copy across 30 mailboxes generates a fingerprint Gmail clusters on. Vary subject and opening line per sender group.

Instantly alerts that matter

Under Settings → Email Notifications, enable:

• Warm-up failing / paused.
• High bounce rate on a campaign.
• Inbox marked as spammy.
• Mailbox disconnected.

Silence everything else. The campaign-level notifications are noise; the account-level ones are signal.

Frequently asked questions