The best email inbox monitoring tools of 2026

GlockApps answers the question most senders have after a campaign: did it reach the inbox, a tab or the spam folder? You send a test email to the GlockApps seed list, and its Inbox Insight report shows where the message landed at each provider. The provider report on its site lists 27, including Gmail, Outlook, Yahoo, AOL, Zoho, Office 365 and Proton Mail, and you can add your own addresses to the seed list. Each test also goes through five spam filters (SpamAssassin, Barracuda, Microsoft Exchange Online Protection, Proofpoint and a Google filter) and comes back with spam scores and notes on your content.

Between tests, GlockApps reads your DMARC reports and runs uptime monitors that check your IPs against major blacklists, as often as every minute on paid plans. Alerts go to email, Telegram, Slack or PagerDuty, and you can connect Google Postmaster Tools data.

The free plan includes 2 spam test credits, DMARC reports for 10,000 messages and 5 uptime monitors, which is enough to try it on a real campaign. Essential costs $85 a month on monthly billing with 30 test credits, or $59 a month billed yearly ($708) with 360 credits. If you test only before big sends, credit packs start at $16.99 for 3 tests.

Mail-Tester is the fastest free check to run before a send. The site gives you an address, you send your email to it, and Mail-Tester scores the message, your mail server and your sending IP. The score is based on SpamAssassin with the sign reversed, so a higher number is better, and the report tells you what is set up properly and what to fix.

You get 3 free tests in any 24 hours, and free results stay online for 7 days, or 30 days with an account that uses your own address prefix. For more tests, packs start at $5 for 10, and subscriptions start at $10 a month for 50 tests, with prices shown before VAT. Paid accounts also get a JSON API and an iframe you can embed.

Mail-Tester checks one message against one address. It tells you whether your email and setup look like spam, but it does not show whether Gmail or Outlook put the message in the inbox. Pair it with a placement test such as GlockApps when you need that answer.

MailReach is built for sales teams that send cold email from several Google Workspace or Microsoft 365 mailboxes and need each one to stay out of spam. Its warm-up sends up to 100 emails a day per mailbox to build a sending history, and its reputation dashboard shows how each mailbox and domain is doing.

The spam test sends your message to more than 30 MailReach mailboxes across Google, Microsoft and Yahoo and reports where it landed. It also checks whether your domain or sending IP is on a blacklist and whether SPF, DKIM and DMARC are set up. You can run 3 free tests in any 24 hours, which makes it a useful second opinion next to GlockApps.

The main plan, which bundles warm-up with the spam tester, costs $19.50 per mailbox a month and includes warm-up, the dashboard, domain and inbox health checks and at least 20 spam test credits; yearly billing saves 20%. One credit buys one inbox placement test with a report. MailReach also sells credits pay as you go, but the calculator on its pricing page did not show a clear price per credit, so check before you buy.

If you send newsletters through an email service rather than from individual inboxes, you will not use the warm-up and can skip MailReach.

Warmy sells warm-up and placement tests together, like MailReach, but splits its plans by the kind of mailbox you send to: B2B Sender for Google Workspace and Microsoft 365 recipients, and B2C Sender for Gmail, Yahoo and Outlook. Placement tests report whether a message reached the inbox, spam or the Promotions tab, and Warmy says its seed list holds more than 500,000 US addresses.

Plans start from $49 a month. Warmy prices warm-up by volume and asks you to confirm your monthly allowance of placement tests with its team, so get the numbers in writing before you sign up. The 7-day free trial needs no card, and Warmy also offers a free deliverability test, free blacklist, DNS, SPF, DKIM and DMARC checkers, and a free 30-minute deliverability review with one of its staff.

Warmy fits teams that send both cold outreach and marketing email and want one vendor for both. If you only need placement tests, GlockApps publishes clearer limits.

MxToolbox suits whoever looks after your domain and mail server and wants to hear about a problem before customers do. The free plan checks one domain against blacklists once a week, which catches a listing but not quickly.

Delivery Center costs $129 a month and covers 5 domains and 500,000 messages. It adds adaptive blacklist monitoring for your own servers and the third-party services that send for you, monitoring of inbound and outbound mail flow, DMARC reports with SPF and DKIM configuration checks, complaint reporting, BIMI management and 30 inbox placement analyses a month. Delivery Center Plus costs $399 a month for 5,000,000 messages, raises placement analyses to 100 a month and adds SPF flattening, which helps when your SPF record runs into its lookup limit.

MxToolbox shows only monthly prices. Its placement analyses are a smaller part of the package than at GlockApps, so pick MxToolbox when monitoring and alerts matter more to you than testing each campaign.

Postmaster Tools is Google's own report on how Gmail treats mail from your domain, based on your real sends rather than test mailboxes. After you verify your sending domain, its dashboards show your spam rate, reputation, authentication results and delivery errors for mail sent to @gmail.com and @googlemail.com addresses. A compliance status dashboard shows whether you meet Gmail's email sender requirements. Google treats anyone sending about 5,000 or more messages to Gmail accounts in 24 hours as a bulk sender.

It has two limits. It covers personal Gmail addresses only, and Google leaves days blank when you send too little mail for it to report without exposing individual users. You sign in with a Google account or a Google Workspace account; the help pages we read list no price.

Microsoft runs a similar service for Outlook.com called SNDS, which gives IP owners data on each of their IPs and reports when users mark messages as junk. Set up both, then use a paid tool such as GlockApps to cover other providers and to get alerts.

Validity Engage is now where Validity sells inbox placement testing, and the old Validity Everest page redirects to it. Engage also includes Litmus: Litmus's pricing page now says "Litmus is now part of Validity Engage." That puts placement testing, design checks and monitoring under one contract.

Engage tests placement across more than 90 email providers and breaks results out by provider, IP and domain. It tracks your Sender Score across IPs and domains around the clock, alerts you when an IP or domain is blocklisted with guidance on getting removed, and checks SPF, DKIM and DMARC alignment. The email creation side finds rendering errors across more than 100 email clients and runs checks before you send. Other parts of the platform cover live email monitoring, competitor research and contact data quality.

Validity publishes no prices. Its pricing page says "Enterprise pricing, built to fit" and asks for your goals and volume before it builds a plan, and the way in is a demo. Engage makes sense for a brand with a deliverability or email operations team; a small business will get what it needs from GlockApps for far less.

Inbox Monster sells to brands whose email programs are big enough to have separate creative, QA, marketing and deliverability people, and it names all four as its audience. Alongside testing, its Monster Search and Monster Boards tools let you research other brands' emails before you plan your own. Its Deliverability Suite covers inbox placement, spam traps and reputation with ongoing monitoring, and its SMS Suite reports whether your text messages reach customers, which none of the other tools here offers.

The prices are published and they are large: the Deliverability Suite starts at $15,000 a year and the SMS Suite at $6,000 a year. A separate Creative Suite for email previews, including dark mode, starts at $3,750 a year for 15,000 previews. Inbox Monster mentions no trial; you book a demo, and it offers custom pricing.

Consider it alongside Validity Engage if you send at enterprise volume and want text message delivery checked by the same vendor. Anyone sending a weekly newsletter should start with GlockApps.