The best email deliverability tools cover four jobs: inbox tests, blocklist monitoring, DMARC reports and list verification. Here are eight that do.

An email that lands in spam doesn't bounce. Nobody gets an error. Often the only sign is a click rate that slowly sags.

Email deliverability tools tell you why. You need one for each of four jobs: a placement or spam test before you send (GlockApps, Mail-Tester), reputation and blocklist monitoring after you send (Google Postmaster Tools, MxToolbox), DMARC reports showing who sends as your domain (Postmark DMARC Digests, dmarcian), and list verification before you import old addresses (ZeroBounce, Kickbox). All eight have a free start.

Gmail and Yahoo now set rules every sender has to meet.

Since 1 February 2024, Google has required a baseline from everyone sending to personal Gmail accounts, and more from anyone sending over 5,000 messages a day to them. Miss the rules and your email "might not be delivered as expected, or might be marked as spam" (Google).

Source: Google: Email sender guidelines, read 27 October 2026.

Treat 0.3% as a ceiling. The same page tells senders to keep spam rates "below 0.10%" and to "avoid ever reaching a spam rate of 0.30% or higher", and recommends SPF, DKIM and DMARC for every domain, whatever the volume.

Yahoo's rules match closely: SPF or DKIM and a spam rate below 0.3% for everyone; for bulk senders, SPF and DKIM, a passing DMARC policy of at least p=none, one-click unsubscribe, and unsubscribes honored within 2 days (Yahoo Sender Hub).

We ranked each tool on five things that decide inbox placement.

1. How close it is to the source. Data straight from a mailbox provider ranks first; after that, tools covering more than one of the four jobs rank higher.

2. A free start a small sender can use today, without a sales call.

3. How it bills, and whether the entry price fits a list of a few thousand to 10,000 contacts.

4. Setup effort: a DNS record, a test address or an upload.

5. Whether it says what to fix: the record, the blocklist or the address, not just a score.

Spreeflo isn't ranked: it isn't a deliverability tool.

These are the eight email deliverability tools worth a look.

1. Google Postmaster Tools

Our pick to set up first: Google's own view of your mail.

Postmaster Tools shows how Gmail sees the mail you send to personal Gmail accounts. The spam rate in Google's rules is the one "reported in Postmaster Tools", so this is the number you're graded on.

• What it checks: spam rate, domain and IP reputation, authentication and delivery errors, for mail to @gmail.com and @googlemail.com addresses.

• Pricing: Google's help pages list no fee. You need a Google or Google Workspace account and a domain verified with a TXT or CNAME record.

• Free start: Google's pages list no paid tier. Google warns data "might be missing if the total number of messages for a given day is too low", so a small list may see empty charts.

• Best for: anyone who emails Gmail users, which is nearly everyone.

Microsoft's equivalent for Outlook.com, SNDS, shows data per sending IP, but you can only request access to "the IPs for which you are responsible", and access expires 10 months after approval. It's only useful if you control your own sending IPs.

2. GlockApps

Best all-rounder: seed tests, DMARC reports and reputation monitors in one account.

GlockApps sends your email to test inboxes at different mailbox providers and reports where it landed: Inbox, Tabs, Spam or Missing. The same report gives a SpamAssassin score, checks your sending IP against major blocklists and checks SPF, DKIM and DMARC. Every plan also processes DMARC reports and includes IP reputation monitors.

• Pricing: Essential is $59 a month billed annually ($708 a year) for 360 spam-test credits, 600,000 DMARC messages and 10 IP reputation monitors. Growth is $99 a month ($1,188 a year), Enterprise $129 ($1,548) (GlockApps pricing). These are annual-billing prices; the page has a monthly toggle but showed no separate monthly price when we checked.

• Free start: a free plan with 2 spam-test credits, 10,000 DMARC messages, unlimited DMARC domains and 1 IP reputation monitor.

• Best for: a regular sender who wants placement tests and DMARC in one tool.

3. Mail-Tester

Best free pre-send check: one email, one score.

Mail-Tester gives you an address; you send your email to it, and it analyses "your message, your mail server, your sending IP" and shows what's configured properly and what isn't. Its spam check is an out-of-the-box SpamAssassin install (FAQ).

• Pricing: one-off packs from $5 for 10 tests ($80 for 1,000), or monthly plans from $10 for 50 tests ($80 for 2,000), excluding VAT. Paid accounts add a JSON API, white labelling and a 30-day history (Mail-Tester pricing).

• Free start: 3 free tests in any 24 hours, no account needed. Free results stay up for 7 days.

• Best for: checking a new template or a DNS change before a big send.

4. Postmark DMARC Digests

Best first DMARC tool: a readable weekly email instead of XML files.

Once you publish a DMARC record, mailbox providers send you aggregate reports as XML. Postmark's DMARC tool turns them into "human-readable weekly email summaries", sent every Monday once your DNS is verified.

• Pricing: free, or $14 a month per domain for a web dashboard, all mail sources and IPs, 60 days of history, and weekly and monthly reports.

• Free start: the free digest covers your top 10 mail sources (5 IPs each) with 7 days of history. The paid tier has a 14-day free trial.

• Best for: a founder publishing DMARC for the first time who wants to see if anything is spoofing the domain or failing alignment.

5. MxToolbox

Best blocklist monitoring: a free weekly check, and a full suite when you need it.

MxToolbox Delivery Center monitors blocklists for your domain. Its paid plans add inbox placement analysis, complaint reporting, DMARC reports, SPF/DKIM/DMARC configuration analysis, mail flow monitoring and BIMI management.

• Pricing: Delivery Center is $129 a month for 5 domains, 30 placement analyses a month and 500,000 emails. Delivery Center Plus is $399 a month for 100 analyses and 5,000,000 emails, with SPF flattening.

• Free start: weekly blocklist monitoring for 1 domain.

• Best for: the free weekly blocklist check; the paid suite suits agencies.

6. ZeroBounce

Best verification with extras: list cleaning plus a placement test and blocklist monitor.

ZeroBounce checks addresses before you send. It flags invalid, disposable and inactive addresses, identifies spam traps, abuse emails and catch-alls, and scores valid and catch-all addresses from 1 to 10. The same account offers an inbox placement test, monitoring of 200+ blocklists with alerts, and a DMARC monitor.

• Pricing: pay as you go from $39 for 2,000 addresses, or ZeroBounce ONE from $99 a month, starting at 10,000 credits that roll over (ZeroBounce pricing). Unknown results and duplicates cost nothing.

• Free start: 100 validation credits a month, 1 inbox test, 1 email server test and 1 blocklist monitor scanned every 24 hours, refilled monthly.

• Best for: cleaning a list you haven't emailed in a while, with a free daily blocklist check on the side.

7. Kickbox

Best pay-as-you-go verification: a published price for every volume.

Kickbox verifies whether each address is deliverable and refunds the credit when it can't give a definite result. It says a 100,000-address list takes about an hour.

• Pricing: $10 for 1,000 verifications, $40 for 5,000, $70 for 10,000, $150 for 25,000 and $500 for 100,000. Above 1 million is custom. These are list prices; a 30%-off promo code was running through 1 December when we checked.

• Free start: 100 free verifications.

• Best for: a one-off clean before importing an old list into a new tool.

8. dmarcian

Best for moving DMARC to enforcement across several domains.

dmarcian is a full DMARC platform: aggregate (RUA) report processing and SPF and DKIM inspection tools on every plan, while forensic (RUF) report processing and alerts are left out of the free Personal plan. It's the step up when you want to move from p=none to quarantine or reject without blocking a legitimate sender.

• Pricing: Basic is $24 a month, or $19.99 a month billed annually ($239.88 a year), for 2 domains and 100,000 DMARC-capable messages a month. Plus is $240 a month ($199 annually) for 8 domains, 1,000,000 messages and 3 users.

• Free start: a 30-day trial with no card. The free Personal plan is for non-business use only.

• Best for: a business with several domains that wants an enforced DMARC policy.

Also checked, not ranked: NeverBounce charges $8 per 1,000 verifications pay as you go, or $49 a month for up to 10,000; we preferred Kickbox's full published price list. EasyDMARC starts at $44.99 a month ($35.99 annually) with a no-card trial but lists no free plan, and keeps inbox placement testing on a custom-priced plan. Valimail has a free Monitor tier; its paid plans are priced on request.

Here is what each tool checks and how it bills.

Prices and free starts from each vendor's own pages, read on 27 October 2026, in US dollars.

Which tool you need depends on what's going wrong.

• Clicks fell and nothing bounced. Check spam rate and reputation in Postmaster Tools, then run a GlockApps test to see which providers filter you.

• A new template or domain. Send it to Mail-Tester first.

• Bounces jumped after an import. Stop sending to that list and verify it with Kickbox or ZeroBounce.

• You don't know who else sends as your domain. Publish DMARC at p=none and read Postmark's free digest. Move to dmarcian when you're ready to enforce.

• A customer says your email never arrived. Check the blocklist monitors on MxToolbox (weekly) or ZeroBounce (daily), both free.

For a 10,000-contact list, an illustrative first year using the prices above: the free tools cost $0; adding one Kickbox clean of 10,000 addresses makes it $70; adding GlockApps Essential for regular placement tests makes it $778.

What Spreeflo handles built in.

Spreeflo is an email marketing platform, so it doesn't run seed tests, read DMARC reports or verify addresses against mail servers. It does handle the routine list hygiene that keeps those tools quiet:

• A Suppression list on every plan. Campaigns, journeys and broadcasts skip suppressed addresses, and imports leave them out.

• Spam and disposable domain cleaning. Contacts on about 87,000 known spam or disposable domains, refreshed daily, are marked Cleaned and never emailed, checked on arrival and again at send.

• Sending-reputation alerts. By default, admins get an email when bounces pass a 3% warning level or complaints pass 0.1%, and again at the 5% and 0.2% lock levels. A campaign whose own rates climb too high pauses itself and tells the admins.

• Recommended subdomains per stream, like send.example.com for marketing and notify.example.com for transactional, to protect your main domain's reputation.

• A domain setup guide for SPF, DKIM and DMARC.

See it in Spreeflo: the complaint warning sits at the same 0.1% Google advises staying under, so you hear about a problem long before Gmail's 0.3% ceiling. Read the domain setup guide →

This is the setup every sender needs before any tool.

No tool fixes a missing record. Do these once, and most of the tools above will simply confirm you're fine.

1. Send from your own domain, ideally a subdomain, never a free Gmail or Yahoo address.

2. Publish SPF and DKIM with the records your email provider gives you. Google requires one for all senders and both above 5,000 a day; set up both anyway. Use a DKIM key of at least 1024 bits (Google recommends 2048).

3. Publish DMARC at p=none, with reports going to a tool like Postmark's free digest.

4. Verify your domain in Postmaster Tools.

5. Offer one-click unsubscribe with a visible link, and honor it within 2 days.

6. Only email people who asked. Google recommends confirming each address before subscribing it, and considering unsubscribing people who don't open or read your messages.

7. Test before big sends, and verify any list you haven't emailed in months.

The broader point.

Deliverability is mostly a list problem in a technical costume. The records take an afternoon. What keeps you in the inbox after that is emailing people who want to hear from you, and stopping before the quiet ones press "spam". For a small team, that has to run on its own.

Build this in Spreeflo

Spreeflo runs suppression, spam-domain cleaning and bounce and complaint alerts in the background, and segments with unlimited AND/OR conditions find the contacts who've gone quiet so you can win them back or stop emailing them. Sending starts on Starter at $16 a month, 2 to 3x more affordable than Mailchimp, and the free plan (forms and web analytics, no card) lets you start collecting subscribers first.

See plans and pricing → · Set up your sending domain

These are the questions people ask about email deliverability tools.

What is an email deliverability tool?

Software that tells you whether your email reaches the inbox, and why not. Most do one of four jobs: test placement before you send, monitor reputation and blocklists, process DMARC reports, or verify the addresses on your list.

How do I test email deliverability?

Send your email to a seed-testing tool like GlockApps, which reports whether it landed in Inbox, Tabs or Spam, or went missing, at different mailbox providers. For a free email deliverability test of content and server setup, use Mail-Tester (3 free tests in 24 hours).

What is the best free email deliverability checker?

Google Postmaster Tools for your real Gmail spam rate and reputation, and Mail-Tester for a pre-send check. Add Postmark's free DMARC digest and MxToolbox's free weekly blocklist check, and three of the four jobs are covered without paying (27 October 2026).

Do I need an email deliverability service?

Usually not a paid one. If your domain is authenticated, your spam rate stays under 0.1% and bounces are low, free tools are enough. Pay for placement testing or a DMARC platform when you send at volume, run several domains, or have a problem the free tools can't explain.

Do I need DMARC if I send fewer than 5,000 emails a day?

Google only requires it above 5,000 messages a day to Gmail, but recommends SPF, DKIM and DMARC for every domain. A p=none record doesn't block anything, and its reports show who is sending as your domain.

How often should I verify my email list?

Before you import a list into a new tool, and before emailing any segment you haven't mailed in months. Day to day, confirmed opt-in and automatic bounce suppression do most of the work.

Read these next.

• Email marketing for small business: the five automations to set up first

• Email newsletter templates: 30 free layouts and when to use each

• Email Marketing Bible, chapter 9: land in the inbox

• Email marketing automation: how it works, with 6 journeys to copy

Sources

• Google: Email sender guidelines, read 27 October 2026

• Yahoo Sender Hub: best practices, read 27 October 2026

• Google: Postmaster Tools and Postmaster Tools help, read 27 October 2026

• Microsoft SNDS, read 27 October 2026

• GlockApps pricing and inbox email tester, read 27 October 2026

• Mail-Tester, FAQ and pricing, read 27 October 2026

• Postmark DMARC, read 27 October 2026

• MxToolbox Delivery Center, read 27 October 2026

• ZeroBounce and ZeroBounce pricing, read 27 October 2026

• Kickbox pricing, read 27 October 2026

• dmarcian pricing, read 27 October 2026

• NeverBounce pricing, EasyDMARC pricing and Valimail pricing, read 27 October 2026