Email Deliverability Test: The Full Pre-Send Email Spam Test Stack, in Order

An email deliverability test is not one tool. It is six checks run in order: authentication, blacklists, content, inbox placement, sender reputation and warmup health. If you only have ten minutes, run a seed-list email spam test such as MailReach's free spam test, which covers several of those checks in one report; our MailReach review explains what that tool does and where it stops.

Some tool links here are affiliate links (disclosure). Nerdy Joe is a MailReach affiliate. We have no relationship with GlockApps, Mail-Tester or MXToolbox.

We did not run hands-on tests of any tool for this guide. Tool facts come from each vendor's own pages as of November 2026, sender rules come from Google's and Yahoo's official pages, and sources are listed at the end.

The pre-send test stack at a glance

Run the steps in this order. There is no reason to tune copy on a domain that fails DKIM.

Email spam test vs email deliverability test

People use "email spam test", "spam checker" and "email deliverability test" for the same need: will this email reach the inbox.

The useful distinction is scope. A spam test looks at one message: its content, its setup and where it lands. A deliverability test also covers blacklists, real recipient complaints and mailbox history, so this guide treats the spam test as steps 3 and 4 of the stack.

What Google and Yahoo require from senders

Every test below maps back to published rules. Google's requirements have applied since February 1, 2024, and Google defines a bulk sender as one that sends more than 5,000 messages a day to Gmail accounts. Yahoo's page does not put a number on "bulk sender".

Two details matter for cold email. Google's page also says "Don't send messages to people who didn't sign up to get messages from you", so passing every technical check does not make unsolicited mail welcome at Gmail. And Yahoo says it calculates spam rate based on mail delivered to the inbox.

Step 1: Test authentication (SPF, DKIM, DMARC)

Authentication proves the mail really comes from your domain, and a failure here outweighs everything else.

• SPF lists the servers allowed to send for your domain. Check that the record exists, that there is only one, and that it includes every service that sends for you.
• DKIM signs each message with a key published in DNS. Google says sending to personal Gmail accounts requires a DKIM key of 1024 bits or longer.
• DMARC tells receivers what to do when SPF and DKIM fail, and requires the From: domain to align with one of them. A policy of p=none satisfies both Google and Yahoo for bulk senders.
• Reverse DNS and TLS. Both Google and Yahoo ask for valid forward and reverse DNS, and Google asks for TLS.

How to check

Lookup tools read the DNS records for a domain you type in. Send-based tools ask you to send a real email and then read the headers, which also proves the records pass on live mail.

MailReach's free SPF checker and DKIM checker are the send-based kind. Per MailReach, you insert a code in an email and send it to its test addresses, and the report also covers DMARC, blacklist status, reverse DNS and MX.

Check every sending domain, not just the main one; our cold email infrastructure guide covers that setup.

Step 2: Check blacklists

A blacklist (or blocklist) is a public list of domains and IPs associated with spam, and receiving servers consult some of them.

Check three things: the sending domain, the sending IP, and every domain you link to in the email.

MailReach's spam test reports whether the domain or sending IP is blacklisted and whether links have blacklist hits, and its warmup plan lists domain and inbox health checks that include blacklists. MailReach does not publish which lists it checks or how often. MXToolbox lists a free plan with weekly blacklist monitoring for 1 domain.

A listing is a symptom. MailReach's help center says "MailReach can't remove you from blacklists", and no testing tool can: you fix the cause, then ask the list operator for removal.

Step 3: Test content and spam words

With the plumbing confirmed, test the message. Filters look at wording, links, images and code, and so should you.

• Wording. Paste the subject and body into our free spam word checker and rewrite the phrases it flags.
• Links. Count them, make sure none are broken or insecure, and avoid URL shorteners. MailReach recommends a custom tracking domain that matches the sending domain.
• Images and HTML. Heavy templates and a high image-to-text ratio read as marketing mail. Cold email usually does better as plain text.

For a single-message score, Mail-Tester is a free option: you send to a generated address and get a score out of 10 from a SpamAssassin-based check. MailReach's spam test lists content checks for spam words, links, attachments, images, tracking pixels and HTML complexity.

A content score is a rule-based estimate, since no mailbox provider publishes its filter, which is why the next step exists.

Step 4: Run an inbox placement test

This is the step most people mean by "email spam test". You send the real email to a seed list of mailboxes at several providers, and the tool reports whether each copy landed in the inbox, spam, a tab such as Promotions, or went missing.

The short version of the method:

1. Use the exact email you plan to send, from the same sending tool and domain.
2. Add the tool's test code to the body and send to the full seed list.
3. Read the result by provider, with professional inboxes (Google Workspace, Microsoft 365) separated from personal ones.
4. Test a plain email with no links or tracking as a control, so you know whether content or setup is at fault.
5. Change one thing and re-test.

Our inbox placement test guide covers seed lists, reading results by provider and a tool comparison in full. If you plan to use MailReach for this step, the MailReach spam test guide goes through its score and limits.

MailReach says its test sends to 30+ mailboxes across Google, Microsoft and Yahoo and that a 90% or higher inbox placement rate is considered strong. You can run a free MailReach test up to 3 times per 24 hours without a credit card, per MailReach, as of November 2026.

Step 5: Check sender reputation in Postmaster Tools

Steps 1 to 4 are lab tests. Sender reputation is what happened to the mail you already sent to real people.

Google Postmaster Tools is the official source for that at Gmail. Google says it shows spam rate, reputation, message authentication and delivery errors for mail sent to personal Gmail accounts. To set it up you need a Google account, you add your DKIM or SPF domain, and you verify it with a TXT or CNAME record in DNS.

Watch the spam rate first. Google's line is below 0.10% and never 0.30% or higher, and it reflects real recipient reports, which no seed list can simulate.

Know its limits. Postmaster Tools covers personal Gmail accounts only (addresses ending in @gmail.com or @googlemail.com), so it says nothing direct about Microsoft, Yahoo or a prospect's corporate mailbox. Google also says data might be missing when a day's message volume is too low, so a small B2B sender can see empty charts.

If it shows a rising spam rate or a falling reputation, pause and fix targeting before the next campaign, whatever the seed test says.

Step 6: Check warmup health

A new mailbox on a new domain has no sending history, and Google's guidelines tell senders to increase sending volume slowly. Warmup tools automate a ramp by exchanging email with a network of other inboxes.

In MailReach, each mailbox gets a Reputation Score out of 100 that appears 72 hours after connecting, and MailReach says 90 or higher is the target. MailReach recommends at least 14 days of warmup on a new mailbox or domain before any campaign.

MailReach says the score is based on where warming emails land and is not an indicator of whether an address is ready for campaigns. It also states that "you can have a perfect sender reputation and still land 100% in spam", because content and sending setup matter too.

On warmup itself, Google's sender guidelines recommend increasing volume slowly to engaged recipients and do not mention warmup tools, and Gmail's program policies prohibit automating Gmail in ways that mislead or deceive users. MailReach says Google has not banned warmup and that it follows provider rules, and Google has not published a position on warmup networks specifically, so treat automated warmup as a practice Google neither endorses nor explicitly names.

For how warmup, daily health checks and resting mailboxes fit together in a running system, see our post on mailbox warmup and inbox placement.

Free vs paid email deliverability test tools

You can run the whole stack for free once. Paid tools earn their price when you repeat it across many mailboxes, keep history, or want alerts.

When free is enough, and when to pay

Free tools cover a sender with 1 or 2 mailboxes or a one-time setup check on a new domain. Paying makes sense when you manage many mailboxes or client domains, want scheduled tests with alerts, or need history to show whether a change helped.

MailReach puts warmup and testing on one bill, priced per mailbox, so the cost grows with mailbox count. Our MailReach pricing guide has the math.

• Best for one free all-round check: MailReach's free spam test, since one send returns placement, content and authentication results.
• Best for a content-only score: Mail-Tester.
• Best for real Gmail complaint data: Postmaster Tools.

If per-mailbox warmup pricing does not suit you, sequencers such as Instantly, Smartlead and PlusVibe include warmup in the sending plan, and our roundup of the best email warmup tools compares the options.

What to do when a test fails

Fix failures in stack order: authentication first, then blacklists, content and reputation.

If everything looks green and the email still lands in spam, MailReach points to three suspects: sending reputation, spam words the test did not detect, or the sending tool itself (its IP or tracking domain). Its suggested check is a short two-sentence plain email sent without a sending tool.

If the plain email also lands in spam, slow down. MailReach's guidance for a reputation drop is to reduce or pause campaign sending, keep bounces under 5%, limit follow-ups to 2, and only then raise warmup volume.

Email deliverability test checklist

• [ ] SPF record exists, is the only one, and includes every sending service
• [ ] DKIM passes on a real sent email, with a key of 1024 bits or longer
• [ ] DMARC record is published (p=none at minimum) and the From: domain aligns
• [ ] Sending domain, sending IP and every linked domain are clear of blacklists
• [ ] Subject and body passed a spam word check
• [ ] Links are few, working, secure and not shortened; tracking uses a custom domain
• [ ] The real email was sent to a seed list from the real sending tool and read by provider
• [ ] Postmaster Tools is verified for the domain and spam rate is below 0.10%
• [ ] New mailboxes have warmed for at least 14 days and warmup stays on
• [ ] Marketing and subscribed messages carry one-click unsubscribe, and opt-outs are honored within 2 days
• [ ] The list is verified, with bounces expected under 5%

Rather not build the list yourself?

Building a verified list, warming mailboxes and watching placement every week is the rest of the work. Nerdy Joe is owned by Agency Growth Partners (AGP), and AGP builds verified lists and runs outbound for agencies.

If you would rather hand that off, book a call with David.

Bottom line

A real email deliverability test is a sequence: authentication, blacklists, content, placement, reputation, warmup health. Most of it can be done free, and the two checks no shortcut replaces are a seed-list placement test before you send and Postmaster Tools after.

To cover the placement step today, start with MailReach's free spam test. If you are weighing its paid warmup and test credits, the full MailReach review lays out pricing, strengths and the limits to know first.

Sources

• Gmail Help: Email sender guidelines
• Gmail Help: Gmail Program Policies
• Google Workspace Admin Help: Postmaster Tools
• Yahoo Sender Hub: Sender best practices
• MailReach: Email spam test
• MailReach: Email deliverability test
• MailReach: Pricing
• MailReach: SPF checker
• MailReach: DKIM checker
• MailReach: Homepage
• MailReach: How email warmup works
• MailReach blog: Warmup Inbox pricing
• MailReach blog: Email warmup solutions, in-house vs third-party services
• MailReach Help: Getting started after connecting an email account
• MailReach Help: How to get the highest reputation score
• MailReach Help: Why am I still landing in spam with a high reputation score
• MailReach Help: How to help fix a spam spike or reputation score drop
• MailReach Help: My domain is blacklisted
• GlockApps pricing
• Mail-Tester
• Mail-Tester FAQ
• Mail-Tester account plans
• MXToolbox Delivery Center