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Side-by-side comparisonBy the Warmy deliverability team Updated
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Warmy brings Adeline AI, personalized warm-up, real link clicks, inbox placement testing, verification and reputation monitoring together in one all-in-one deliverability platform.
Email on Acid’s pricing FAQ identifies Mailgun Inspect as its successor and says subscription customer transitions begin in June 2026. Current plans are branded Mailgun Inspect.
Email on Acid is succeeded by Mailgun Inspect; transitions begin June 2026 according to the official FAQ.
Key takeaways
Good to knowWarmy goes beyond a single email tool: Adeline AI, warm-up, testing, monitoring and verification work together to improve your deliverability.
Warmy brings ongoing optimization, actionable intelligence and deliverability measurement into one platform. See how that broader coverage compares with the specialist capabilities below.
| Feature | Warmy | Email on Acid |
|---|---|---|
| Primary focus | All-in-one, self-serve email deliverability infrastructure | Email on Acid’s pricing FAQ identifies Mailgun Inspect as its successor and says subscription customer transitions begin in June 2026. Current plans are branded Mailgun Inspect. |
| Best-fit audience | Teams improving and measuring sender reputation across their existing sending stack. | Inspect accepts HTML, a hosted URL or a message submitted from an ESP. Users review renderings, collaborate and fix HTML before rerunning checks. |
| Client previews | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Basic includes previews across supported clients and devices. |
| Unlimited seats | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | All plans include unlimited users. |
| API access | Documented API included on every plan | Published on all plans. |
| Light/dark comparison | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Dual light and dark mode comparison view. |
| Collaboration | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Comments and collaboration tools. |
| Accessibility tests | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Premium and Contract feature. |
| HTML analysis | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Premium and Contract code analysis. |
| Link validation | Built-in | Premium and Contract feature. |
| Image validation | Built-in | Premium and Contract feature. |
| Spam content checks | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Premium and Contract content checks. |
| Inline editor | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Premium and Contract HTML editor. |
| Versioning | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Premium and Contract version history. |
| HTML submission | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Test content can be supplied as HTML. |
| URL submission | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Can test from a hosted email URL. |
| ESP test submission | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Can send a test from the ESP. |
| Preview profiles | Warmy focuses on reputation, placement testing and monitoring; this specialist capability is not presented as an equivalent Warmy feature. | Saved device/client selections control preview consumption. |
| Pricing and billing | From $49/month, billed monthly | Current Mailgun Inspect prices, not historical Email on Acid tiers; displayed $ currency code unverified. Preview-allotment subscription |
| Trial and free access | Seven days, no credit card required | Basic and Premium advertise one month free. |
The detailed analysis
Inspect accepts HTML, a hosted URL or a message submitted from an ESP. Users review renderings, collaborate and fix HTML before rerunning checks.
Email on Acid’s pricing FAQ identifies Mailgun Inspect as its successor and says subscription customer transitions begin in June 2026. Current plans are branded Mailgun Inspect.
Keep the legacy slug for discovery, but quote the current Inspect offering. Do not list Email on Acid and Inspect as competing current subscriptions or silently carry forward old preview allowances.
Inspect accepts HTML, a hosted URL or a message submitted from an ESP. Users review renderings, collaborate and fix HTML before rerunning checks.
This fits an email production team validating a finished template or transactional notification. Rendering correctness and content checks are different from production sending or observing all subscribers’ inbox folders.
Basic includes previews, API access and collaboration, while Premium adds accessibility, HTML analysis, link/image validation, spam checks and editor/versioning. All plans list unlimited users.
Evaluate the defects you actually need to catch before selecting the entry tier. Basic’s preview access should not be described as including every automated QA check advertised for the platform.
Mailgun documents usage by individual client/device rendering, not by whole email test. Subscription allowances reset monthly, while contract allotments are annual.
Selecting many clients can consume many previews in one test. Use saved preview profiles for representative coverage and account for reruns; the advertised preview allotment is not an equal number of full multi-device test runs.
Inspect is integrated in the Mailgun account experience, and the welcome guide explains access, team invitations and supported submission routes. Migration is described separately on the legacy product site.
A shared account experience does not establish that Inspect pricing includes outbound delivery volume or inbox-placement monitoring. Confirm migration steps, billing and any separately ordered Mailgun services rather than treating them as free Inspect entitlements.
Warmy describes an active warm-up mechanism using gradual volume increases and conversational engagement. Inspect’s official scope instead centers on previewing, checking and fixing email content before send.
Choose Inspect for visual QA and accessibility checks, and evaluate Warmy for its described warm-up workflow. A dark-mode screenshot and a reputation-building conversation address different failure modes.
The Warmy advantage
From Adeline’s next-step guidance to real engagement and provider-level measurement, Warmy connects the work that separate email tools leave to your team.
Adeline connects authentication, DNS, inbox placement, blocklists, content, engagement and provider signals into one picture. She builds personalized deliverability plans, detects spam risk and explains what to change next.
Personalized timing, volume and pacing, with gradual ramp-up and engagement that includes opens, replies, important markings and moving messages out of spam.
Warmy’s engagement includes real clicks on your links, alongside opens and other natural mailbox interactions.
1M+ real, protected Google Workspace, Microsoft 365, and B2C mailboxes
500,000+ real US seed accounts, desktop and mobile; rotated monthly; speeds up warmup
Included: 5–50 tests/month by tier, with automated testing. Provider-level results distinguish inbox, Promotions and spam, so you can measure progress instead of relying on SMTP acceptance alone.
Domain/IP reputation tracking, blacklist alerts, spam-placement reports
SPF, DKIM, and DMARC tracking, record checks, and DMARC report analysis
Direct Google Postmaster integration
Check address validity as part of the wider deliverability workflow, alongside reputation work, placement testing and monitoring.
AI template optimization, custom warm-up topics and templates, and conversations in 30+ languages.
Multiple mailboxes and domains; 100 to 5,000 warmup emails/day by plan. Auto-archive keeps warm-up conversations out of your working inbox.
Klaviyo, Mailchimp, HubSpot, SendGrid, ActiveCampaign, Google Workspace, Microsoft 365, and SMTP. Self-serve setup in minutes via OAuth or SMTP/IMAP.
Documented API included on every plan. 24/7 human support; dedicated CSM and deliverability consultant on Expert/Platinum.
Allowances and dedicated support vary by plan. Plans starting from $49 / month.
Plans and total cost
| Pricing detail | Warmy | Email on Acid |
|---|---|---|
| Starting price | $49/ month | Current Mailgun Inspect prices, not historical Email on Acid tiers; displayed $ currency code unverified. |
| Billing | Monthly | Preview-allotment subscription |
| Free trial | Seven days, no credit card required | Basic and Premium advertise one month free. |
| Also included | Adeline AI, warm-up, placement tests, monitoring, verification and API access; allowances vary by plan. | See the individual features and published plan allowances below. |
Plans starting from $49 / month. See Warmy’s five plans
A mailbox subscription, an address-verification credit, a rendering test and an SMTP sending allowance buy different outcomes. Compare total cost using your own mailbox count, list size, testing frequency and sending volume; do not equate a lower unit price with equivalent coverage.
Social proof
Rated 4.9/5 on G2 and trusted by 35,000+ businesses.
“Warmy has been a game changer for us. The platform pays for itself many times over.”
“If you do cold email, Warmy will increase your efficiency, improve your deliverability, and cut your costs.”
Thomas Tzouridis“I've purchased many marketing tools before. Often, once you buy, you're on your own. With Warmy, they care about you.”
The verdict
| If you want… | Choose |
|---|---|
| Everything in one platformWarm-up, placement tests, verification, authentication and reputation monitoring in one connected workflow. | Warmy |
| Adeline AI expertisePersonalized plans, predictive spam-risk detection and clear next steps from your AI deliverability expert. | Warmy |
| Real engagement and seed accountsA 1M+ mailbox network, real link clicks and 500,000+ US seed accounts. | Warmy |
| Expert help and an easy startSelf-serve setup, API access and 24/7 human support; dedicated consultant options on higher tiers. | Warmy |
| Legacy transition and current product: Email on Acid’s pricing FAQ identifies Mailgun Inspect as its successor and says subscription customer transitions begin in June 2026. Current plans are branded Mailgun Inspect. | Email on Acid |
| Pre-send QA workflow: Inspect accepts HTML, a hosted URL or a message submitted from an ESP. Users review renderings, collaborate and fix HTML before rerunning checks. | Email on Acid |
| Plan-specific QA coverage: Basic includes previews, API access and collaboration, while Premium adds accessibility, HTML analysis, link/image validation, spam checks and editor/versioning. All plans list unlimited users. | Email on Acid |
A practical evaluation
Legacy transition and current product: Email on Acid’s pricing FAQ identifies Mailgun Inspect as its successor and says subscription customer transitions begin in June 2026. Current plans are branded Mailgun Inspect. Keep that objective separate from your sender-reputation and placement baseline.
Test a representative message with a consistent provider mix. Record authentication, inbox and spam placement before changing the sending workflow.
Keep the legacy slug for discovery, but quote the current Inspect offering. Do not list Email on Acid and Inspect as competing current subscriptions or silently carry forward old preview allowances.
Selecting many clients can consume many previews in one test. Use saved preview profiles for representative coverage and account for reruns; the advertised preview allotment is not an equal number of full multi-device test runs. Keep specialist tooling where it serves a separate job. Coordinate any overlapping warm-up schedules instead of doubling engagement volume.
Compare provider-level placement alongside specialist results, bounces and complaints. Address validity, rendering previews and SMTP acceptance alone do not prove inbox placement.
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