Email Deliverability for Outbound Sales

Help the user set up, diagnose, and optimize email deliverability — from domain authentication and warmup through inbox placement, reputation monitoring, and platform-specific configuration. This skill is tool-agnostic and covers Apollo, Mailshake, Salesloft, Lemlist, Yesware, Mixmax, Reply.io, Woodpecker, and standalone tools.

Step 1 — Gather context

Ask the user:

What's your situation?
- A) Setting up a new domain for cold outbound
- B) Warming up a new mailbox / sender account
- C) Emails going to spam — need to diagnose
- D) Open rates dropped significantly
- E) High bounce rates
- F) Blacklisted — need to recover
- G) Scaling sending volume (increasing daily sends)
- H) Switching platforms (migrating senders)
- I) Something else — describe it
What's your current sending setup?
- Primary domain or dedicated outbound domain?
- How many mailboxes / sender accounts?
- Daily sending volume (current or target)?
- How long have you been sending from this domain/mailbox?
What tools are you using?
- A) Apollo.io
- B) Mailshake
- C) Salesloft
- D) Lemlist
- E) Yesware
- F) Instantly / Smartlead
- G) Mixmax
- H) Reply.io
- I) Woodpecker
- J) HubSpot / Salesforce (direct sending)
- K) Custom SMTP / other
- L) Multiple tools — describe
Domain authentication status?
- A) SPF/DKIM/DMARC all configured
- B) Some configured, not sure which
- C) Not configured / don't know
- D) Using a new domain with nothing set up

If the user's request already provides most of this context, skip directly to the relevant step. Lead with your best-effort answer using reasonable assumptions (stated explicitly), then ask only the most critical 1-2 clarifying questions at the end — don't gate your response behind gathering complete context.

Step 2 — Domain authentication framework

Domain authentication is the foundation of deliverability. All three records must be properly configured.

SPF (Sender Policy Framework)

What it does: Tells receiving servers which mail servers are authorized to send on behalf of your domain
DNS record: TXT record on your domain

Format:

v=spf1 include:_spf.google.com include:mailshake.com ~all

Key rules: Only one SPF record per domain. Use
```
include:
```
for each authorized sender. Max 10 DNS lookups.
Common mistake: Multiple SPF records (only the first is read), too many includes (exceeds lookup limit)

DKIM (DomainKeys Identified Mail)

What it does: Adds a cryptographic signature to outgoing emails proving they haven't been tampered with
DNS record: TXT or CNAME record (format varies by provider)
Setup: Each sending platform provides its own DKIM key. Add the record they give you to your DNS.
Common mistake: Not adding DKIM for every sending platform. Each service needs its own DKIM record.

DMARC (Domain-based Message Authentication, Reporting & Conformance)

What it does: Tells receiving servers what to do with emails that fail SPF/DKIM checks
DNS record: TXT record at
```
_dmarc.yourdomain.com
```

Recommended start:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

(monitor mode)

Progression: none → quarantine → reject (move to reject after 2-4 weeks of clean monitoring)
Common mistake: Jumping straight to
```
p=reject
```
before monitoring — this blocks legitimate emails

Custom tracking domain

What it is: A subdomain (e.g.,
```
track.yourdomain.com
```
) for open/click tracking instead of shared tracking domains
Why it matters: Shared tracking domains get flagged by spam filters. Custom domains protect your reputation.
Setup: CNAME record pointing to your platform's tracking server

Verification checklist

SPF record includes all sending services
DKIM configured for each sending platform
DMARC record exists (start with p=none)
Custom tracking domain configured
Test with mail-tester.com (aim for 9+/10)
Test with MXToolbox for DNS record validation

Step 3 — Warmup strategy

New mailboxes and domains must be warmed up before sending at volume. Skipping warmup is the #1 cause of deliverability problems.

Warmup schedule (new mailbox)

Week	Daily sends	Notes
1	5-10	Manual sends to engaged contacts, internal test sends
2	15-25	Mix of warm contacts and small cold batches
3	30-40	Gradual increase, monitor bounce/spam rates
4	40-50	Standard cold outbound volume
5+	50-75	Scale cautiously, never exceed provider limits

For new domains: Add 2 extra weeks at the beginning (weeks 1-2 at 3-5 sends/day). New domains have zero reputation.

Warmup tools

Smartlead Ultra Premium Warmup — AI-driven warmup built into the Smartlead platform with exclusive warmup network. Unlike standalone tools, it's fully integrated with sender management and campaign scheduling.
Instantly — automated warmup with real engagement (opens, replies, moves from spam)
Warmbox — AI-powered warmup network
Lemwarm — Lemlist's built-in warmup (included free with every seat, 10,000+ user network, deliverability scoring)
Mailwarm — Standalone warmup service

These tools simulate real email conversations to build sender reputation. Run warmup for at least 2-3 weeks before adding cold outbound.

Mailbox rotation

Why: Distributing sends across multiple mailboxes protects each one's reputation and increases total volume
Rule of thumb: 1 mailbox per 50-75 cold emails/day
Setup: Connect multiple sender accounts in your platform and enable rotation/round-robin
Naming: Use real names (jane@company.com), not generic addresses (sales@, outreach@)

Step 4 — Platform-specific implementation

In Mailshake

Sending limits: Configure per-sender daily limits in Settings > Senders
Sender rotation: Add multiple senders to a campaign — Mailshake rotates automatically
Custom tracking domain: Settings > Tracking Domain — add CNAME record
Warmup: Mailshake doesn't have built-in warmup. Use Instantly or Warmbox alongside.
Bounce handling: Auto-pauses recipients on hard bounce. Monitor in Activity > Bounces.

In Apollo

Inbox Ramp Up: Settings > Email > Inbox Ramp Up — Apollo's built-in warmup feature
Command Center: Settings > Email > Deliverability — monitors sender health, SPF/DKIM status
Sending limits: Settings > Email > Sending Limits — per-mailbox daily caps
Mailbox rotation: Assign multiple mailboxes to a sequence — Apollo rotates sends
Custom tracking domain: Settings > Email > Custom Tracking Domain

In Salesloft

Email settings: Settings > Email — configure sending windows, throttling, daily limits
Throttling: Salesloft auto-throttles to prevent spikes. Configure max emails per hour.
Sender management: Cadence settings > Sender — assign specific senders per cadence
Custom tracking domain: Admin > Email > Custom Tracking Domain

In Lemlist

Lemwarm: Built-in warmup included with every seat at no extra cost. Enable per email account — set warmup to 30 emails/day for accounts <6 months, 40/day for older. Minimum 3-5 weeks before adding cold outbound. Monitor deliverability score (target 90+).
Inbox rotation: Connect multiple email accounts to a sequence — Lemlist rotates sends automatically. Each account limited to plan allowance (5 per user on Multichannel Expert, $9 per additional inbox).
Domain auth: Configure SPF/DKIM/DMARC and custom tracking domain before launching sequences. Lemlist Help Center has DNS configuration guides.
Sending limits: Configure per-account daily limits. Recommended 30-50 cold emails/day per mailbox.

In Yesware

Sends from your inbox: Yesware campaigns send directly from Gmail/Outlook — no third-party server. This improves deliverability because emails appear as genuine 1:1 messages, not bulk sends.
No built-in warmup: Since Yesware sends from your existing inbox, traditional warmup is less critical. However, if you're sending high-volume campaigns from a new email account, ramp up gradually (20/day → 50/day over 2-3 weeks).
Domain auth: SPF/DKIM/DMARC should still be configured for your domain. Yesware inherits your inbox's auth settings.
Custom tracking domain: Yesware uses its own tracking domain for open/click tracking. This is a shared domain — no custom tracking domain option.
Sending limits: Governed by your email provider (Gmail ~400-500/day, Outlook ~1,000/day) plus Yesware plan limits on campaign recipients.
Key advantage: Inbox-native sending means no separate IP reputation to manage and no relay server that could get blacklisted.
Key limitation: No deliverability dashboard — Yesware doesn't report inbox placement rate, so you won't know how many emails landed in spam vs inbox.

In Smartlead

SmartSenders: Auto-provision mailboxes via Gmail/Outlook OAuth. Configure per-sender daily limits (recommend 30-50/day per mailbox for cold outbound).
SmartInfra: Dedicated IPs with auto DNS/DKIM/DMARC configuration for high-volume senders. Evaluate when sending 1,000+ emails/day or managing multiple clients.
Ultra Premium Warmup: Built-in warmup — enable per mailbox, minimum 2-3 weeks before campaign sends. Monitor warmup reputation score (target 80+ before activating).
SmartDelivery: Inbox placement testing — send test emails to seed accounts and measure inbox vs spam placement. Run before launching campaigns and periodically during active sends.
Custom tracking domain: Settings > Tracking Domain — add CNAME record for branded link tracking.

In Mixmax

Sending method: Gmail-native — emails send through the user's actual Gmail account (Google Workspace), not through Mixmax's servers. This means deliverability is tied to your Google Workspace domain reputation, not Mixmax's infrastructure.
SPF/DKIM/DMARC: Managed at the Google Workspace level, not in Mixmax. Ensure your domain has SPF, DKIM, and DMARC configured in Google Workspace Admin > Apps > Google Workspace > Gmail > Authentication.
Custom tracking domains: Available to reduce spam filtering on tracked links — configure in Mixmax settings. Uses CNAME record pointing to Mixmax's tracking servers.
No built-in warmup: Mixmax does not have a warmup tool. Since it sends through Gmail, use a third-party warmup service (Lemwarm, Warmbox, Instantly) connected to your Google Workspace account if needed.
Sending limits: Subject to Gmail/Google Workspace sending limits (2,000 emails/day for Workspace, 500/day for free Gmail). Mixmax sequences respect these limits automatically.
No deliverability dashboard: Mixmax doesn't have a dedicated deliverability dashboard. Monitor bounce rates in sequence reporting; check Google Postmaster Tools for domain reputation.
Best practice: Since Mixmax is Gmail-native, your Google Workspace domain health IS your Mixmax deliverability. Focus on Google Postmaster Tools, proper authentication, and keeping bounce rates under 2%.

In Reply.io

Built-in warmup: Peer-to-peer warmup service — uses real Reply.io user accounts (no free/temporary emails). The system opens, replies, marks as important, and removes from spam realistically. Enable in Settings > Email Accounts > Warmup.
Warmup timeline: 2-3 weeks for new domains/mailboxes. Leave warmup running even after starting sequences to maintain reputation.
Domain health checker: Dedicated tab in Reply.io that checks SPF, DKIM, DMARC, and MX records. Provides actionable fix suggestions for each issue.
Google Postmaster integration: Reply.io pulls spam rate data directly from Google Postmaster Tools — monitor your spam rate without leaving the platform.
Branded links: Custom tracking domains to replace Reply.io's default tracking domain — reduces spam filtering on tracked links. Configure in Settings > Branded Links.
Sending limits: Respects Gmail/Outlook provider limits; configure per-mailbox daily caps. Use multiple mailboxes (up to 10/user on Multichannel plan) to increase volume safely.
Bounce handling: Automatic bounce detection; bounced contacts are paused in sequences. Monitor bounce rate in sequence analytics — keep under 3%.
Best practice: Enable warmup on every new mailbox before adding it to sequences. Use the domain health checker weekly. If spam rate exceeds 0.3% in Google Postmaster, pause sequences and investigate.

In Woodpecker

Built-in warmup: Free warmup powered by Mailivery — AI-driven interactions (opens, replies, marks as important, removes from spam). Starts with a few emails/day, ramps to max 50/day. Included in all plans (free plan: 4 warmup slots). Additional slots available at €5/account.
Bounce Shield: Proactive protection that prevents sending to risky or invalid addresses before they bounce. Reduces bounce rate and protects sender reputation automatically.
Adaptive Sending: Automatically adjusts sending volume and pace based on email provider limits and engagement signals. Prevents overloading mailboxes and triggering spam filters.
ESP Matching: Matches your sending patterns to what email service providers expect from legitimate senders — improves inbox placement.
Email verification: Free catch-all verification powered by Bouncer. Real-time list cleaning validates prospect emails when added to campaigns. Catches invalid addresses before sending.
Domain audit: In-app tool that checks SPF, DKIM, DMARC configuration with actionable fix suggestions. Run before launching any campaign.
Spam checker: Pre-send analysis that highlights spammy words, broken links, and authentication issues in your email content.
Deliverability monitor: Ongoing monitoring of inbox placement and sender reputation. Alerts when metrics degrade.
Inbox rotation: Distributes sends across multiple mailboxes to stay within per-account limits while maintaining volume. Unlimited email accounts on all plans.
Best practice: Woodpecker has the most comprehensive built-in deliverability toolkit of any cold email tool. Enable warmup + Bounce Shield + Adaptive Sending on every account. Run domain audit before first campaign. Use the spam checker on every new email template.

Standalone tools (any platform)

MXToolbox: DNS lookup, blacklist check, SPF/DKIM/DMARC validation
mail-tester.com: Send a test email, get a deliverability score (aim for 9+/10)
SmartDelivery (Smartlead): Inbox placement testing by provider (Gmail, Outlook, Yahoo)
GlockApps: Inbox placement testing and spam filter analysis
Google Postmaster Tools: Monitor Gmail-specific reputation (if targeting Gmail recipients)
Microsoft SNDS: Monitor Outlook/Microsoft reputation

Step 5 — Monitoring and recovery

Key metrics to track

Metric	Target	Action if exceeded
Bounce rate	<3%	Pause sending, clean list, verify emails before next send
Spam complaint rate	<0.1%	Reduce volume, review content, check targeting
Open rate	>40%	Check deliverability (inbox vs spam), test subject lines
Unsubscribe rate	<1%	Review frequency, improve relevance

Blacklist check and delisting

Check: Use MXToolbox blacklist check or multirbl.valli.org to check your domain/IP
Common blacklists: Spamhaus, Barracuda, SORBS, SpamCop, CBL
Delisting process: Each blacklist has its own removal request form. Fix the root cause first (high bounces, spam complaints), then request removal.
Timeline: Most blacklists delist within 24-48 hours after request. Spamhaus can take longer.

Reputation recovery

If your domain reputation is damaged:

Stop all outbound from the affected domain/mailbox immediately
Diagnose: Check bounce rate, spam complaints, blacklist status
Fix root cause: Clean list, fix auth, reduce volume
Warmup again: Treat the mailbox as new — follow the warmup schedule from Week 1
Consider a new domain: If reputation is severely damaged (blacklisted on 3+ lists), it may be faster to start a new outbound domain

List hygiene

Verify before sending: Use NeverBounce, ZeroBounce, or BriteVerify before importing lists
Remove on bounce: Hard bounces should be permanently removed, not just paused
Re-verify periodically: Email addresses decay at ~25% per year. Re-verify lists older than 3 months.
Never use purchased lists: Purchased lists have high bounce/spam rates and will destroy your reputation

Gotchas

Don't skip warmup. Every new mailbox needs 2-4 weeks of warmup before cold outbound. Sending 100 cold emails from a brand-new mailbox will land in spam immediately. Claude often generates "connect mailbox → start sending" workflows that skip this critical step.
Don't send from your primary domain. Use a dedicated outbound domain (e.g.,
```
outbound.yourcompany.com
```
or
```
yourcompanymail.com
```
). If your outbound domain gets blacklisted, your primary domain (and all company email) is protected.
Don't ignore bounces. A bounce rate above 3% signals to email providers that you're sending to bad addresses. This damages reputation quickly. Pause the campaign, clean the list, and re-verify before resuming.
Don't use purchased or scraped lists. These lists have high bounce rates, spam traps, and unengaged recipients. They will destroy your sender reputation within days. Always build lists from legitimate data providers and verify emails before sending.

Related skills

```
/sales-cadence
```
— Design outbound cadence strategy and content
```
/sales-smartlead
```
— Smartlead platform help (SmartSenders, SmartInfra, SmartDelivery, campaigns)
```
/sales-lemlist
```
— Lemlist platform help (sequences, Lemwarm, enrichment, LinkedIn automation)
```
/sales-mailshake
```
— Mailshake platform help (campaigns, Lead Catcher, settings)
```
/sales-apollo-sequences
```
— Apollo sequence mechanics and configuration
```
/sales-salesloft
```
— Salesloft platform help
```
/sales-agency-outbound
```
— Multi-client agency outbound — infrastructure, client isolation, warmup at scale
```
/sales-yesware
```
— Yesware platform help (inbox-native sending, campaigns, tracking)
```
/sales-mixmax
```
— Mixmax platform help (for Mixmax-specific setup)
```
/sales-reply
```
— Reply.io platform help (for Reply.io-specific setup)
```
/sales-woodpecker
```
— Woodpecker platform help (for Woodpecker-specific setup)
```
/sales-email-tracking
```
— Email engagement tracking — understand open/click accuracy and privacy limitations
```
/sales-enrich
```
— Verify and enrich contact emails before sending
```
/sales-prospect-list
```
— Build prospect lists with verified contacts
```
/sales-do
```
— Not sure which skill to use? The router matches any sales objective to the right skill.

Examples

Example 1: New domain setup

User says: "I'm setting up a new domain for cold outbound. What do I need to do?" Skill does:

Recommends a dedicated outbound domain (separate from primary)
Provides SPF/DKIM/DMARC setup instructions with example DNS records
Outlines the warmup schedule (weeks 1-5)
Recommends warmup tools and verification steps Result: User has a complete domain setup and warmup plan

Example 2: Diagnosing a deliverability drop

User says: "My open rates dropped from 45% to 15%. I'm using 3 Apollo mailboxes at 50 emails/day each." Skill does:

Identifies likely causes: reputation damage, blacklisting, or auth issues
Provides a diagnosis checklist: check blacklists, verify SPF/DKIM/DMARC, review bounce rate
Recommends volume reduction and mailbox-by-mailbox reputation check
Creates a recovery plan with timeline Result: User has a diagnosis framework and recovery plan

Example 3: Platform migration

User says: "Switching from Apollo to Mailshake. What do I need to do for deliverability?" Skill does:

Verifies domain auth is platform-independent (SPF/DKIM may need updating for Mailshake)
Recommends adding Mailshake to SPF and configuring Mailshake-specific DKIM
Advises warmup for new platform connection even if mailbox is established
Compares sending limit configuration between platforms Result: User has a migration checklist covering auth, warmup, and platform config

Troubleshooting

Emails landing in spam

Symptom: Recipients report emails in spam, or open rates are very low (<15%) Cause: Missing/broken domain auth, poor sender reputation, content triggers, or shared tracking domain Solution: Run full auth check (SPF/DKIM/DMARC). Test with mail-tester.com. Set up custom tracking domain. Check blacklists. If reputation is damaged, reduce volume and re-warmup.

High bounce rate

Symptom: Bounce rate above 3% Cause: Unverified email list, stale data, or sending to catch-all domains Solution: Immediately pause affected campaigns. Run remaining list through email verification (NeverBounce, ZeroBounce). Remove all invalid addresses. Only resume with verified addresses.

Blacklisted domain

Symptom: Widespread delivery failures, MXToolbox shows blacklist hits Cause: High bounce rate, spam complaints, or sending to spam traps Solution: Stop all sending. Identify and fix root cause. Submit delisting requests to each blacklist. Wait 24-48 hours. Re-warmup before resuming. If severely blacklisted, consider a new outbound domain.

sales-deliverability

NPX Install

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