Email TesterDeliverability Suite
Mail-tester + MXToolbox — in one button, right where you work

Email Tester & Deliverability Checker

Instant DNS audit (SPF, DMARC, MX, DKIM, BIMI, MTA-STS), real email header analysis, bulk-sender compliance for Gmail / Outlook / Yahoo 2025, RBL monitoring, and DMARC report visualization — all in your browser, no signup required for the core checks.

0
server resources on free checks
DNS-over-HTTPS
25
DKIM selectors probed
auto-discovery
15+
RBLs checked per IP
blacklist scan
12
compliance rules
Google/MSFT/Yahoo
Why this, not mail-tester? Context, not tabs — audit a domain by clicking on any site; analyze the real email you just received without forwarding it anywhere; get a compliance verdict against Gmail's Nov 2025 enforcement for free.
Tier 2 · Live test

Send us a test email

Generate a unique address, send your campaign to it, and get a full deliverability audit — authentication, blocklists, content, unsubscribe compliance and delivery timing.

We'll generate a one-time address on our inbound mail server. Send your email to it from the exact setup you want to test (ESP, CRM, or your own MTA).

Domain DNS Audit

Audit any domain's email security

SPF, DMARC, MX, DKIM, BIMI, MTA-STS, and TLS-RPT — fetched live via DNS-over-HTTPS and scored against bulk-sender best practices.

Try

Enter a domain above and click Audit domain to start.

Header Analyzer

Deep email header analysis

Paste raw RFC 5322 headers — get the full forensic breakdown: DKIM h= coverage, RFC 8058 one-click unsubscribe, ESP detection, alignment, and spam scores.

Paste raw email headers
Copy the full header block from your email client's "show original" / "view source" view. The body is not required.

Paste raw email headers above and hit Analyze

Or click Load sample to see a full forensic breakdown on a realistic example.

Bulk sender compliance

Will your mail be delivered in 2026?

Point-by-point compliance verdict against Gmail (Feb 2024 + Nov 2025 permanent 550 enforcement), Microsoft (May 2025 + Apr 2026 550 5.7.515), and Yahoo (mirrors Google).

Compliance inputs
Enter the sending domain plus a couple of operational facts. We audit 12 enforcement points across Gmail, Microsoft, and Yahoo.
Try:

No compliance verdict yet

Enter a sending domain above and run the check to see a 12-point audit against Gmail, Microsoft, and Yahoo enforcement rules.

Reputation & Reports

Blacklist & DMARC reports

Check IP/domain reputation against 17 RBLs and visualize DMARC aggregate reports for authentication trends and abuse signals.

RBL / Blacklist Checker
Check an IP and/or domain against 15 IP-based RBLs and 2 domain blocklists.

At least one of IP or domain is required.

Enter an IP and/or domain above, then click Check blacklist to scan 17 RBLs.

DMARC Aggregate Report Viewer
Paste a rua XML report to visualize alignment, failures, and source breakdowns.

Paste a DMARC aggregate (rua) XML report, or click Load sample to try one with a mix of pass/fail records.

Free toolbox

Generators & quick utilities

Build correct DNS records instead of debugging them by hand — plus SPF flattening, exact DKIM lookup, spam-copy scanning, and your recent audits.

SPF Record Builder
Compose a valid SPF record — we handle the syntax, you paste it into DNS.
Terminator:
DNS lookups used:0 / 10
DNS host: @ · type TXT
v=spf1 -all

Publish this as a TXT record at your domain root (@). Only ONE SPF record per domain — merge, never add a second.

DMARC Record Wizard
Start with p=none to monitor, then ramp to quarantine → reject.
DNS host: _dmarc.example.com · type TXT
v=DMARC1; p=none;

Then analyze your incoming aggregate reports in the DMARC Reports section below, and ramp p= once you're confident legitimate mail aligns.

BIMI Record Generator
Show your logo next to messages in Gmail / Apple Mail / Yahoo.
DNS host: default._bimi.example.com · type TXT
v=BIMI1;

Requirements: DMARC at p=quarantine or p=reject, logo as SVG Tiny Portable/Secure, and a Verified Mark Certificate (VMC) for Gmail.

Three surfaces, one product

Where you actually work — not another tab to open

The extension lives in three places. Each is tuned to the task at hand: a quick glance in the popup, a deep read beside an email in the sidebar, and the full dashboard in a new tab.

instantly.ai/campaign/abc-123
You're viewing instantly.ai
Click the extension icon →
Email Testerinstant audit
Active domain
instantly.aiaudited
72
Good with warnings
2 critical, 4 warnings
SPF record
DMARC p=reject
DKIM (2 selectors)
MTA-STS
RFC 8058 unsubscribe
BIMI logo

Domain auto-detect

Reads the domain of the active tab — click the toolbar icon, get an instant verdict. No copy-paste.

DNS-over-HTTPS, zero backend

All free checks run client-side via DoH. No server cost, no signup, no rate limits on you.

1-click deep dive

“Open in New Tab” hands the full domain off to the dashboard for SPF/DKIM/DMARC/DKIM-h coverage analysis.