# Clay and Instantly deliverability guide

URL: https://www.inboxplease.com/learn/clay-instantly-deliverability-guide

Clay and Instantly are excellent at what they are built for. Neither tool manages your sender reputation. Neither tells you whether your emails are landing in inboxes. That gap is where deliverability problems start — and this guide is how you close it.

Category: AI & Deliverability · By Chris Aylott · Sep 27, 2026 · 5 min read

## Key takeaways

- Clay and Instantly are excellent for list building and sending at scale, but neither monitors your sender reputation or tells you whether your emails are landing in inboxes.
- Before scaling a sequence, confirm SPF, DKIM and DMARC pass, warm any domain under 30 days old, run a placement test, ramp volume gradually and clean the list.
- Keep cold outreach on domains separate from your primary business domain, so a damaged outreach domain can be retired and replaced while the primary domain stays untouched.

## What these tools do — and don't do

Clay is purpose-built for building highly targeted, enriched prospect lists. It connects dozens of data sources, runs enrichment waterfalls, and lets you create precisely filtered contact databases that would take weeks to assemble manually. For list quality, it is genuinely best in class.

Instantly is purpose-built for running multi-domain cold email sequences at scale. It handles domain rotation, follow-up sequencing, reply detection, and sending infrastructure in a way that makes high-volume cold outreach operationally manageable. For execution, it is similarly best in class.

What neither tool does: monitor your sender reputation at Gmail, Outlook, or Yahoo. Tell you what percentage of your emails are landing in inboxes versus spam folders. Alert you when a sending domain gets blacklisted. Verify that authentication is correctly configured on a real delivered message. These are the variables that determine whether the outreach you built with Clay and Instantly actually reaches anyone.

## The specific risks with each tool

### Clay risks

- **List size velocity**: Clay makes it easy to build 10,000+ contact lists in a day. Sending to a large list without a warmed domain or established reputation causes exactly the engagement signal degradation that damages reputation. List quality is not the same as list targeting precision at the right send volume.
- **Data enrichment is not the same as targeting precision**: Enriched contact data improves personalisation, but it does not guarantee that the contact is relevant to your offer, active, or likely to engage. Low engagement at scale — even from a well-enriched list — is still a negative reputation signal. Hunter.io data from 31 million emails in 2025 shows average cold email reply rates at 4.5%. Even with excellent list quality, most recipients will not engage.

### Instantly risks

- **Multi-domain scale on new infrastructure**: Instantly's infrastructure is optimised for volume. Volume at scale on new or under-warmed domains produces spam folder placement rapidly. The tool does not prevent this — it is the operator's responsibility to ensure domain readiness before scaling into Instantly's full capacity.
- **Warmup pool quality matters**: Instantly operates its own warmup infrastructure. The quality of that network — specifically, whether it consists of real mailboxes with real user histories or synthetic accounts — affects how meaningful the warmup signal is. A warmup score from a synthetic network does not reflect the same thing as a placement result from real Gmail or Outlook inboxes.

## The checklist before scaling

Every team using Clay and Instantly should run through these five checks before launching a sequence at volume. They take minutes. Fixing the problems they uncover after a damaged reputation takes months.

1. 01: **Authentication: SPF, DKIM, and DMARC**: All three must pass on every sending domain. SPF authorises your sending infrastructure. DKIM cryptographically signs each message. DMARC tells ISPs what to do with messages that fail the first two. These have been mandatory for Google and Yahoo bulk senders since February 2024 — a missing DMARC record is not just a best practice gap, it is a compliance failure at the provider level.
2. 02: **Domain warmup**: Any domain under 30 days old needs warmup before campaign volume. New domains have no sending history — ISPs treat them as higher risk by default. Warmup builds that history gradually with controlled send volumes. Skipping warmup on a new domain and sending immediately at Instantly's scale is one of the most reliable ways to permanently damage a domain.
3. 03: **Placement test before launch**: Run a real inbox placement test against Gmail, Outlook, and Yahoo before launching sequences. Not a warmup score — a real provider-by-provider result from actual inboxes. GlockApps H1 2025 showed cold senders landing at 55.8% in Gmail, 28.7% in Outlook, and 44.5% in Yahoo. Knowing your actual numbers before launch lets you address problems before they affect real prospects.
4. 04: **Volume ramp**: Increase send volume gradually — not in a single spike. A sudden jump from 50 to 500 emails per day is a spam signal regardless of content quality or sender reputation. ISPs expect volume to build over time. A graduated ramp over one to two weeks gives reputation signals time to confirm the increased volume is consistent with normal sender behaviour.
5. 05: **List hygiene**: Remove unverified addresses, role-based addresses (info@, admin@, support@), and catch-all domains before sending. Bounces from unverified addresses and spam reports from role-based addresses that nobody reads are both negative engagement signals. Clay's enrichment data can be high quality — but list hygiene is still a separate step that enrichment does not replace.

## Ongoing monitoring

Deliverability is not a one-time check. Between campaigns, three things are worth monitoring continuously:

- **Blacklist status**: A single blacklist listing can halt delivery silently within hours of a spam complaint spike. Blacklist monitoring catches this before you notice it in campaign metrics.
- **Placement results after volume increases**: Run a placement test any time you significantly increase send volume. Reputation changes in response to actual sending behaviour — a result that was acceptable at 200 emails/day may not hold at 2,000.
- **Reply rate trends**: A sustained drop in reply rates with stable copy is more likely a delivery issue than a copy issue. Instantly benchmark data (billions of interactions, 2025) shows average reply rates at 3.43%, down from roughly 8.5% in 2019. If your rates are declining below category averages, placement testing is the diagnostic first step.

## Domain strategy

Keep cold outreach domains separate from your primary business domain. This is one of the most consistently useful pieces of infrastructure advice in cold email operations, and one of the most consistently ignored.

Your primary domain carries your brand reputation across every channel — transactional email, customer communications, product notifications. A cold outreach domain that gets damaged does not need to take the primary domain down with it. The practical setup: primary domain for transactional email and brand communications, separate subdomain or dedicated domain for cold sequences. If the outreach domain gets damaged, you retire it and replace it. The primary domain is untouched.

## Run a placement test before your next sequence

Inbox placement across Gmail, Outlook, and Yahoo. Authentication check on a real delivered message. Blacklist monitoring. 60 seconds, no account required.

Written by [Chris Aylott](https://www.inboxplease.com/founder)

Founder & CEO of InboxPlease. Over a decade building email infrastructure for SaaS businesses; writes about deliverability, inbox placement and sender reputation.