Cold email deliverability is one of those things you only notice when it’s already on fire.

One week you’re getting steady replies, intros, calendar links. The next week it’s like you got shadow banned by the universe. Same copy. Same leads. Same offer.

But the truth is, deliverability drifts. Quietly. And if you wait until your reply rate tanks, you’re already late, because sender reputation takes time to rebuild.

So this is the system I recommend and use.

A simple, boring, 30 minute weekly deliverability audit. Not a “full forensic email infrastructure deep dive” every time. Just a tight routine that catches problems early. Keeps you out of spam. And stops you from guessing.

You can do it with whatever stack you’re using. And if you want an all in one place to run warmup, verify lists, rotate inboxes, throttle sends, and keep an eye on reputation signals, that’s basically what PlusVibe is built for. More on that later, but this audit works either way.

However, it's important to note that email deliverability is not a single metric. It’s a bunch of small signals adding up.

This weekly audit is meant to:

• Catch early warning signs before performance drops hard
• Prevent “slow decay” of new inboxes and domains
• Keep list quality from poisoning your sender reputation
• Make sure your sending behavior still looks human
• Identify when you need to pause, throttle, or split traffic

It is not meant to:

• Replace a one time proper setup (SPF, DKIM, DMARC, tracking domain, etc)
• Diagnose every provider specific issue with perfect accuracy
• Fix a totally nuked domain in 30 minutes

Still. If you do this every week, you will avoid most disasters.

The 30-minute weekly deliverability audit (overview)

Here’s the flow. I’ll break each step down, with exactly what to check and what “good” looks like.

Minute 0 to 5: Inbox and bounce sanity check
Minute 5 to 10: List quality and verification spot check
Minute 10 to 15: Spam placement test (quick and dirty)
Minute 15 to 20: Sender reputation signals and blacklists
Minute 20 to 25: Sending behavior check (volume, ramp, rotation, throttling)
Minute 25 to 30: Content triggers check and small fixes

And then you log it. Tiny notes. Trend over time. That’s where the power is.

Before you start: create a one-page audit sheet (seriously)

If you don’t write it down, you’ll “feel” like deliverability is fine until it isn’t.

Make a simple doc or spreadsheet with these columns:

• Week of
• Inboxes used (domains + mailbox count)
• Sends/day average
• Bounce rate %
• Spam complaints (if visible)
• Open rate (optional, only if you trust it)
• Reply rate %
• Spam placement test result (Primary/Promotions/Spam)
• Blacklist check (clear/not clear)
• Notes / changes made

That’s it.

You want direction, not perfection.

Minute 0 to 5: inbox and bounce sanity check

Start with what your ESP or outreach tool is already telling you.

1) Check hard bounce rate (and don’t rationalize it)

Hard bounces are reputation poison. Especially in cold outreach.

Targets:

• Ideal: under 1%
• Acceptable: 1% to 2%
• Risky: 2% to 3%
• Stop and fix: over 3%

If you’re over 3% this week, don’t keep sending like nothing happened. You’re basically paying to damage your domain.

What to do immediately if bounces spike:

• Pause sending on the worst performing inbox
• Verify the last imported list again
• Check if you accidentally included catch alls or risky sources
• Make sure you’re not hitting old leads repeatedly

2) Scan for patterns in bounces

Not all bounces are equal.

Look for keywords in bounce reasons:

• “User unknown” means the address is bad. List problem.
• “Mailbox full” is usually fine, but can stack up.
• “Blocked” / “Rejected” can mean reputation or content issue.
• “SPF fail” / “DKIM fail” is setup. Fix immediately.
• “550 5.7.1” often points to spam filtering.

If you’re using PlusVibe, you’ll usually spot this faster because you can see bounce categories and manage multiple inboxes in one place. But again, any platform can work as long as you’re looking.

3) Check your inbox for replies AND weird stuff

Open your sending inboxes (at least 2 to 3 of them) and scan for:

• Reply volume suddenly down
• Auto replies bouncing back (fine)
• Abuse warnings from Google or Microsoft (not fine)
• “Message couldn’t be delivered” notices
• Threads where prospects say “this is spam” or “stop emailing me”

If you see direct spam complaints in replies, that’s a content/targeting issue, not just deliverability.

Add a note for later.

Minute 5 to 10: list quality and verification spot check

Most deliverability issues are list issues wearing a disguise.

You can have perfect DNS records and still land in spam if you keep sending to bad addresses.

4) Spot check your newest leads

Pull a sample of 20 to 50 leads you added this week.

Check:

• Are these real companies?
• Are you emailing personal inboxes (gmail, yahoo) unintentionally?
• Are job titles wildly off?
• Are domains weird, parked, or obviously fake?
• Are you scraping lists with outdated data?

This takes 2 minutes and saves months of pain.

5) Verify the next week’s list, not last week’s

The move is to keep tomorrow clean, not just explain yesterday.

If you aren’t verifying, start. Period.

You want:

• Remove invalids
• Flag risky / accept all / unknown
• Reduce hard bounces before they happen

If you’re doing this at scale, PlusVibe’s bulk email verification is handy because it’s built into the same outbound workflow. No duct taping three tools together.

Image suggestion (add to your post): a simple screenshot of a verification dashboard or a “Valid / Invalid / Risky” breakdown.

(Replace with your actual media URL once uploaded in WordPress.)

6) Decide your “risky” policy and stick to it

This part is personal, but you need rules.

Example policy:

• Valid: send
• Risky: only send if domain is strong and role is likely correct, otherwise skip
• Catch-all: send but throttle and watch bounces
• Unknown: don’t send
• Invalid: never

The worst thing you can do is change your rules based on how much you want more leads this week.

Minute 10 to 15: spam placement test (quick and dirty)

This is the part everyone skips because it feels annoying. But it’s the fastest way to catch silent filtering.

You don’t need a perfect lab setup. You just need a consistent test.

7) Send a test email to seed accounts

Have 3 to 5 seed inboxes. Ideally:

• 1 Gmail
• 1 Google Workspace (your own domain)
• 1 Outlook.com
• 1 Microsoft 365 (your own domain)
• Optional: Yahoo

Send your latest cold email (exact subject + body) from one of your active sending inboxes.

Check where it lands:

• Primary inbox
• Promotions/Other tabs
• Spam/Junk
• Not delivered

Do this for 2 sending inboxes if you have time, especially if you rotate many.

Targets:

• Healthy: lands in inbox most of the time, maybe Promotions sometimes
• Warning: hitting Promotions/Other consistently across providers
• Bad: any consistent spam placement

To ensure your emails land in the right folder, it's essential to understand how to test email deliverability.

8) If it lands in spam, don’t immediately rewrite everything

First ask:

• Is this one inbox or all inboxes?
• Is it just one provider?
• Did this start after a list import?
• Did you increase volume?
• Did you add links or change tracking?

Spam placement is often behavior and reputation. Not just copy.

Image suggestion: seed inbox results example.

Minute 15 to 20: sender reputation signals and blacklists

Ok. Now we check the “are we getting cooked” signals.

9) Google Postmaster Tools (if you qualify)

If you send enough volume to Gmail and you’ve set it up, Google Postmaster Tools gives you:

• Domain reputation
• IP reputation (if applicable)
• Spam rate
• Authentication status (SPF/DKIM/DMARC)
• Delivery errors

If you see domain reputation drop (High to Medium, Medium to Low), treat it like a real incident.

A weekly check is enough for most teams.

10) Microsoft SNDS (if relevant)

Microsoft visibility is more annoying, but worth checking if you send a lot to Outlook/Office365 recipients.

Look for:

• Complaint rates
• Filtering signals
• IP reputation if you control it

11) Quick blacklist scan

You can use common blacklist checkers. The goal is not to obsess over every tiny list. The goal is to catch obvious problems.

If you’re on a major blacklist, pause and investigate before sending more.

Also note: many cold email setups use shared infrastructure indirectly. So blacklist results can be confusing. Still worth checking weekly.

Targets:

• Clear across major lists
• If listed, identify if it’s your domain, your sending IP, or a shared issue

Minute 20 to 25: sending behavior check (volume, ramp, rotation, throttling)

Deliverability loves boring. It loves consistency.

What kills you is when you act like a robot with a credit card.

12) Check send volume per inbox (and week over week change)

For each mailbox, look at:

• Avg sends/day
• Max sends/day
• Week over week change

If you ramped too fast, slow down.

General cold email safety ranges (not universal, but decent baseline):

• New inbox (weeks 1 to 2): 5 to 15/day
• Warmed inbox (weeks 3 to 5): 20 to 40/day
• Stable inbox: 40 to 80/day depending on your setup, copy, and list quality

If you’re doing 150/day per inbox and “it worked before”… yeah it works until it doesn’t.

For further insights on optimizing your email deliverability beyond these tips, consider exploring some of the top email deliverability tools in 2024 which can provide additional resources and strategies for improving your email performance.

13) Check rotation and throttling

If you use multiple inboxes, rotation is your friend. But only if it’s done right.

You want:

• Even distribution
• Randomized delays
• Business hours sending (or at least not 3am blasts)
• Throttles that prevent spikes

This is one reason platforms like PlusVibe exist. Multi inbox management, rotation, throttling, warmup. It’s the boring infrastructure stuff that keeps you alive at scale.

Image suggestion: inbox rotation / throttling settings.

14) Check warm-up status (and whether you should pause it)

Warmup is not “set and forget forever”.

Weekly check:

• Are warmup emails being delivered and replied to?
• Any warmup inboxes getting warnings?
• Are you warming up inboxes that are already mature, but now sending low volume? (Sometimes fine, sometimes unnecessary.)

If a mailbox is struggling, it can be smart to:

• Reduce cold volume
• Keep warmup running lightly
• Fix list quality
• Then ramp back

A “secure email warm-up” system helps here because you can adjust gradually without messing up real outreach. Again, that’s something PlusVibe focuses on.

Minute 25 to 30: content triggers check and small fixes

This is where people go off the rails and rewrite their whole sequence every week.

Don’t do that.

Just check for obvious deliverability landmines.

15) Links, tracking, and domains

Ask:

• Did you add a new link?
• Is it a shortened link?
• Is it pointing to a domain with poor reputation?
• Are you using too many links?

A safe default for cold email:

• 0 to 1 link max
• Prefer plain text
• Consider no link in first email, link in follow up

Also, if you’re tracking opens with a pixel, understand that:

• Open tracking can hurt deliverability in some setups
• Apple Mail privacy makes opens unreliable anyway

So don’t chase open rate. It’s a trap metric now.

16) Spammy phrases and formatting

You don’t need to write like a monk. But certain patterns trigger filters.

Quick scan:

• Too many exclamation points
• ALL CAPS
• Heavy HTML
• Big images
• “FREE”, “ACT NOW”, “GUARANTEE” style copy
• Weird spacing, invisible characters, copied templates

Also. If your email reads like it was generated and blasted to 10,000 people, recipients behave accordingly. They delete, ignore, mark as spam. That behavior feeds reputation.

17) Personalization that doesn’t look fake

Bad personalization hurts you more than no personalization.

Examples of personalization that backfires:

• “I loved your recent post” with no post referenced
• Incorrect company name merge tags
• Broken variables like “Hi {first_name}”
• Random irrelevant facts stuffed in

If you’re using AI personalization, keep it grounded. Tight. Specific. And correct.

Platforms like PlusVibe position AI personalization and A/B testing as part of the outbound workflow, which is helpful, but only if your data is clean.

What to do when you find a problem (simple decision tree)

Because the audit is useless if you don’t know what action to take.

If bounce rate is high

Do this:

• Stop sending to unverified leads
• Reverify the next batch
• Remove risky categories for a week
• Reduce sends per inbox by 30 to 50% temporarily

If spam placement is creeping up

Do this:

• Reduce volume
• Remove links for a week
• Use a simpler first email
• Improve targeting (fewer “cold” cold prospects)
• Check if one inbox is the problem. Pause it.

If domain reputation dropped

Do this:

• Pause or heavily throttle
• Focus on warmup and positive engagement
• Only send to highest quality leads for 1 to 2 weeks
• Consider moving cold volume to a secondary domain if needed

If everything looks “fine” but replies are down

This is usually not deliverability.

It’s:

• offer
• targeting
• timing
• message market fit
• list freshness

Don’t blame deliverability for copy that doesn’t land.

For improving your email deliverability, consider these strategies:

1. Regularly clean your email list to remove unresponsive or invalid emails.
2. Optimize your email content and subject lines to increase open rates.
3. Monitor your sender reputation and take steps to improve it if necessary.

The weekly audit in practice (a real-ish example)

Let’s say you run 8 inboxes across 2 domains.

This week your numbers look like:

• Bounce rate: 2.6% (up from 0.9%)
• Seed test: Gmail primary, Outlook junk
• Replies: down 30%
• Blacklists: clean

That screams list quality + Microsoft filtering sensitivity.

Action for next week:

1. Reverify leads, remove risky and unknown entirely.
2. Reduce sends to Outlook heavy segments.
3. Throttle overall volume 30%.
4. Remove link from first email.
5. Rotate inboxes more evenly.
6. Run warmup on the worst inboxes.

Then next week you look again. You don’t panic. You just steer.

That’s the whole mindset.

If you're dealing with cold emails, it's crucial to follow cold email best practices such as personalizing your emails, keeping them concise, and following up appropriately without being intrusive.

A few deliverability myths that waste time

Myth 1: “If SPF/DKIM/DMARC are set, deliverability is solved”

Nope. That’s table stakes.

Reputation and recipient behavior matter more day to day.

Myth 2: “Open rate proves inbox placement”

Not reliably anymore. Apple and Google both mess with opens. And some spam filters still “open” emails.

Use seed tests and bounce patterns instead.

Myth 3: “More inboxes always fixes deliverability”

More inboxes can help distribute volume, but if your list is dirty, you’re just spreading damage.

Myth 4: “Warmup fixes everything”

Warmup helps build reputation. It does not override bad targeting, high bounces, or spam complaints.

The simple setup that makes this audit easier

If you’re doing cold outreach seriously, you eventually want:

• Bulk email verification (so bounces don’t wreck you)
• Secure warmup (so new inboxes don’t start cold)
• Multi inbox rotation and throttling (so you can scale without spikes)
• Deliverability optimization and monitoring
• Campaign building, personalization, A/B testing, analytics

That’s basically the checklist PlusVibe is built around. If you want an all-in-one platform that focuses specifically on keeping emails out of spam while scaling outbound, it’s worth a look: PlusVibe.

Not because tools magically fix deliverability. They don’t.

But because the right tool makes the boring discipline part easier to actually do every week.

A 30-minute weekly deliverability audit checklist (copy/paste)

Use this as your recurring task. To make your audit easier, consider incorporating these email deliverability best practices into your strategy.

Moreover, having a structured email deliverability checklist can significantly streamline your process.

However, it's essential to be aware of common email deliverability issues that could hinder your efforts.

Lastly, utilizing effective email deliverability tools can further enhance your chances of success.

Inbox and bounces (0 to 5 min)

• Hard bounce rate this week under 2%
• No SPF/DKIM/DMARC related bounce errors
• No provider warnings (Google/Microsoft) in inbox

List quality (5 to 10 min)

• Spot check 20 to 50 new leads for obvious junk
• Verify next week’s leads
• Remove invalid and unknown, decide how to treat catch all and risky

Spam placement (10 to 15 min)

• Send latest email to 3 to 5 seed accounts
• Record where it lands (Inbox/Promotions/Spam)

Reputation and blacklists (15 to 20 min)

• Check Postmaster (if set up) for rep trend
• Check Microsoft signals (if applicable)
• Blacklist check: clear

Sending behavior (20 to 25 min)

• Volume per inbox stable week over week
• Rotation even, throttling on, delays natural
• Warmup healthy for new or recovering inboxes

Content triggers (25 to 30 min)

• Links minimal (0 to 1), no shorteners
• No heavy HTML or spammy formatting
• Personalization variables correct, no broken merge tags

Wrap up

Deliverability isn’t something you “set up once”. It’s more like brushing your teeth. If you stop, you don’t instantly lose them. But you will.

Do this 30-minute audit every week and you’ll catch problems when they’re still small.

And if you want to make the whole process smoother, like warmup, verification, inbox rotation, throttling, campaign automation, all living in one place, take a look at PlusVibe here: https://plusvibe.ai

That’s it. Put the audit on your calendar. Next Monday, same time.

FAQs (Frequently Asked Questions)

What is cold email deliverability and why does it matter?

Cold email deliverability refers to the ability of your cold outreach emails to successfully land in recipients' inboxes rather than spam folders. It matters because good deliverability ensures steady replies, introductions, and calendar links, while poor deliverability can cause your emails to be ignored or blocked, harming your sender reputation.

Why does cold email deliverability drift over time?

Deliverability drifts quietly due to factors like sender reputation decay, list quality issues, changes in sending behavior, and spam filtering updates. Even with the same copy, leads, and offers, these small signals accumulate and can cause your reply rates to drop unexpectedly.

What is the recommended routine to maintain strong cold email deliverability?

A simple 30-minute weekly deliverability audit is recommended. This includes checking inbox and bounce sanity, list quality spot checks, spam placement tests, monitoring sender reputation signals and blacklists, reviewing sending behavior (volume, ramp-up, rotation), and scanning for content triggers. Logging these findings helps catch problems early and keeps your emails out of spam.

What should I include in a weekly cold email deliverability audit sheet?

Your audit sheet should track: Week of audit; Inboxes used (domains + mailbox count); Average sends per day; Bounce rate percentage; Spam complaints if visible; Open rate (optional); Reply rate percentage; Spam placement test results (Primary/Promotions/Spam); Blacklist status; Notes or changes made. This helps identify trends and directs timely fixes.

How do I interpret bounce rates during my deliverability audit?

Hard bounce rates are critical indicators: under 1% is ideal; 1-2% acceptable; 2-3% risky; over 3% requires immediate action such as pausing sending on problematic inboxes and verifying lead lists. Analyzing bounce reasons like 'User unknown,' 'Blocked,' or 'SPF fail' helps pinpoint whether issues stem from bad lists, setup errors, or content problems.

How can I spot check list quality to prevent deliverability issues?

Regularly sample newly added leads (20-50) to verify they represent real companies with accurate job titles and valid domains. Avoid emailing personal inboxes unintentionally and watch out for parked or fake domains. Ensuring list freshness prevents sending to invalid addresses that poison your sender reputation.