Resource directory
Tools, guides, and references we reach for when something breaks.
SPF blown past 10 lookups, DMARC alignment failures, blocklist listings, complaint-loop setup, Gmail 5.7.x rejects, complaint-rate spikes. Bookmark this. 178 entries across 8 categories, every one used by practitioners who do email deliverability for a living. 12 of them are ours.
Each category pins the one we reach for first.
01Prove who you are
Check, generate, and monitor your SPF, DKIM, DMARC, and BIMI records.
When to reach for thisOpen when alignment fails, SPF blows past 10 lookups, or DMARC reports show an unknown sender as you.
SPF Checker
Check if your SPF record is valid, too long, or missing
MXToolbox SPF Lookup
SPF record lookup with detailed include-chain analysis
SPF Surveyor (dmarcian)
Visual SPF record inspection with lookup count tracking
EasyDMARC SPF Checker
SPF lookup with pass/fail analysis and DNS tree view
Kitterman SPF Validator
Classic SPF syntax validator used by deliverability pros
AutoSPF
Automatic SPF flattening to stay under the 10-lookup limit
DKIM Checker
Verify your DKIM key is published and valid
MXToolbox DKIM Lookup
DKIM record lookup by domain and selector
DKIM Core
DKIM key generator and DNS record builder
mail-tester.com
Send a test email and get a full authentication score
EasyDMARC DKIM Lookup
DKIM record validation with key strength analysis
DMARC Parser
Upload a DMARC XML report and see who sends as you
DMARC Generator
Answer questions, get a DMARC record ready for your DNS
dmarcian
DMARC monitoring platform with aggregate report analysis
EasyDMARC
DMARC deployment and monitoring with smart recommendations
Postmark DMARC Digests
Free weekly DMARC aggregate reports in plain English
MXToolbox DMARC Lookup
Quick DMARC record lookup and policy check
DMARC Analyzer (Mimecast)
DMARC reporting and analysis platform
Valimail Monitor
Free DMARC monitoring used by 90,000+ organizations
URIports
Free DMARC, CSP, and security report aggregation
LearnDMARC
Interactive tool to learn and test SPF, DKIM, and DMARC
parsedmarc
Open-source self-hosted DMARC analyzer with dashboards
BIMI Inspector
Check if your BIMI record is set up correctly
BIMI Group
Official BIMI standard documentation and implementation guide
BIMI Generator (EasyDMARC)
BIMI record lookup and validation
Entrust VMC
Verified Mark Certificates for BIMI logo display
DigiCert VMC
VMC provider for BIMI brand logos in inboxes
Sectigo VMC
Affordable VMC certificates for BIMI brand display
MXToolbox
The Swiss Army knife of email DNS diagnostics
The first tab I open on almost every SOS call. If email broke, this usually shows me where.
DNS Lookup
Look up any DNS record type for email troubleshooting
whatsmydns.net
Check DNS propagation across 50+ global servers
dnschecker.org
Global DNS propagation checker with visual map
DNSViz
DNSSEC validation visualization and diagnostics
Google Admin Toolbox
Google dig tool for quick DNS lookups
IntoDNS
DNS health check with email-specific diagnostics
Email Header Analyzer
Paste raw headers and trace your email path to the inbox
Google Header Analyzer
Official Google tool for analyzing email message headers
MXToolbox Header Analyzer
Parse headers with hop-by-hop delay breakdown
Microsoft Header Analyzer
Microsoft SMTP header analyzer with delay detection
Mail Header Analyzer (whatismyipaddress)
Simple header parser showing relay path and source IP
02Know how you stand
Monitor your sender reputation, test inbox placement, and track deliverability health.
When to reach for thisOpen when an ESP delivery report shows a sudden reputation drop or Postmaster Tools turns red.
Google Postmaster Tools
Official Gmail dashboard for domain reputation and spam rates
Free, first party, and it is Gmail telling you what Gmail thinks of your domain. Set it up before you need it.
Microsoft SNDS
Smart Network Data Services for Outlook sender stats
Microsoft JMRP
Junk Mail Reporting Program for Outlook complaint data
Yahoo Postmaster
Yahoo and AOL sender tools and compliance information
Apple Postmaster
Apple iCloud Mail sender guidelines and support
Gmail Feedback Loop
Gmail spam complaint feedback loop for senders
Sender Score
Free IP reputation score from 0 to 100
Cisco Talos Intelligence
IP and domain reputation lookup by Cisco Talos
BarracudaCentral
IP reputation and blocklist lookup from Barracuda
Google Safe Browsing
Check if Google flags a domain as unsafe
IPQualityScore
IP reputation and fraud scoring for email senders
GlockApps
Inbox placement testing with seed list across 30+ providers
Inbox Monster
Deliverability monitoring and inbox placement analytics
Mailtrap
Email testing sandbox with spam score analysis
mail-tester.com
Free email tester scoring authentication, content, and server
Litmus
Email testing, rendering previews, and deliverability insights
Email on Acid
Pre-send email testing with inbox placement predictions
MailGenius
Free email deliverability tester with spam scoring
Everest (Validity)
Full-stack deliverability platform with reputation and placement
EmailConsul
Email deliverability monitoring and alerting platform
Mailor
Deliverability monitoring with real-time inbox tracking
Postmastery
Enterprise deliverability monitoring and consulting
Mailgun Optimize
Inbox placement, blocklist monitoring, and delivery risk detection
SendForensics
AI-powered deliverability analysis with 100+ checks
03When you get listed
Look up blocklist status, understand who runs them, and learn delisting procedures.
When to reach for thisOpen when you got listed and need to find out which list, which IP, and who delisted you.
MultiRBL
Multi-RBL lookup across dozens of DNS-based blocklists
No account, no upsell, dozens of lists in one pass. My second opinion on every listing.
Blocklist Checker
Check your IP or domain against 80+ blocklists at once
MXToolbox Blacklist Check
Check IP or domain against 100+ blocklists
HetrixTools Blacklist Monitor
Automated blocklist monitoring with email alerts
DNSChecker Blacklist Lookup
Free IP blocklist check across major RBLs
Spamhaus
The most influential blocklist. SBL, XBL, PBL, DBL lists
SpamCop
User-reported spam blocklist with automated reporting
Barracuda BRBL
Barracuda Reputation Block List for IPs and domains
Invaluement
Three-list system targeting snowshoe and real-user spam
SURBL
URI/domain blocklist scanning links inside email bodies
Proofpoint (Cloudmark)
Enterprise email security with sender reputation data
Abusix
Abuse intelligence and blocklist services for ISPs
UCEPROTECT
Three-level blocklist (IP, subnet, ASN)
SpamAssassin
Open source spam filter with scoring rules and RBL checks
04Before you hit send
Keep your list clean. Validate addresses, remove risks, and protect your sender reputation.
When to reach for thisOpen before a migration, after a complaint spike, or any time bounce rate creeps past 2%.
ZeroBounce
Email verification with abuse and high-risk address detection
NeverBounce
Real-time and bulk email verification with 99.9% accuracy
Kickbox
Email verification API with deliverability predictions
Hunter.io
Email finder and verifier for outreach
Clearout
Bulk email verification with catch-all detection
MillionVerifier
Budget-friendly bulk email verification
EmailListVerify
Bulk verification with disposable and role-based detection
Emailable
SOC 2 compliant email verification with ESP integrations
DeBounce
Bulk email verifier with SMTP-level checks
Verifalia
GDPR-compliant verification handling up to 40M records
SEAMWhere verification ends
Every verifier in the category above answers one question: does this mailbox accept mail. Useful, and true. Here is the same address through a validator, and through us.
A validator sees
r.okafor@meridianplantco.com
All true. It just stops here.
Review My Emails sees
r.okafor@meridianplantco.com
The mailbox accepts mail, so the validator is right. But nobody behind it has opened anything since March, and addresses that signed up the same week are going quiet together. Valid answered the wrong question. The verdict answers the one you actually have: send, or wait.
05Who carries your mail
Email service providers, transactional APIs, and self-hosted sending infrastructure.
When to reach for thisOpen when picking a sender, moving off a legacy ESP, or splitting marketing from transactional traffic.
Mailchimp
Popular email marketing platform for small to mid businesses
Klaviyo
Email and SMS marketing built for ecommerce
Brevo
All-in-one marketing platform with email, SMS, and chat
ActiveCampaign
Marketing automation with advanced segmentation and CRM
HubSpot
Marketing hub with email, CRM, and analytics
MailerLite
Simple email marketing with a generous free plan
Customer.io
Behavioral email and messaging platform for product teams
Iterable
Cross-channel marketing platform for enterprise brands
Braze
Enterprise customer engagement platform across channels
Omnisend
Ecommerce marketing automation with email and SMS
Constant Contact
Beginner-friendly email marketing with event tools
Kit (ConvertKit)
Email marketing platform designed for creators
GetResponse
Email marketing suite with webinars and landing pages
beehiiv
Newsletter platform for creators with monetization tools
Postmark
Transactional email with industry-leading delivery speed
When a client cannot afford to lose a receipt or a password reset, this is where I point them.
SendGrid
Email API for transactional and marketing email at scale
Mailgun
Email API with powerful deliverability tools for developers
Amazon SES
Cost-effective email sending at massive scale via AWS
SparkPost (MessageBird)
High-volume email delivery with predictive analytics
SMTP2GO
Reliable SMTP relay with email tracking and analytics
Elastic Email
Affordable email API with built-in deliverability tools
Resend
Modern email API built for developers with React support
Mailjet
Email API with real-time collaboration editor
MailerSend
Transactional email and SMS API built for teams
Mandrill
Mailchimp transactional email add-on
Postfix
The most widely deployed open source mail server
KumoMTA
Modern high-performance MTA built in Rust
PowerMTA
Enterprise MTA for high-volume email delivery
Halon
Scriptable MTA platform for email infrastructure
GreenArrow
On-premise MTA with deliverability monitoring built in
Exim
Flexible open source MTA popular with cPanel hosting
Haraka
High-performance Node.js SMTP server with plugin system
Postal
Open-source mail delivery platform for inbound and outbound
Stalwart Mail
All-in-one Rust mail server with IMAP, JMAP, POP3, SMTP
Maddy
Single-binary mail server replacing Postfix + Dovecot
06Stay legal, stay welcome
Stay on the right side of GDPR, CAN-SPAM, CASL, and evolving email regulations.
When to reach for thisOpen before launching in a new region, before legal review, or when a complaint rate breaches sender requirements.
CAN-SPAM Act (FTC)
Official FTC guide to CAN-SPAM compliance for businesses
GDPR Official Text
Full GDPR text with plain-language explanations
CASL (Canada)
Canadian Anti-Spam Legislation requirements
RFC 5321 (SMTP)
The SMTP protocol specification
RFC 7489 (DMARC)
DMARC protocol specification
RFC 6376 (DKIM)
DKIM Signatures specification
RFC 7208 (SPF)
Sender Policy Framework specification
Gmail Sender Guidelines
Official Gmail requirements for bulk senders
The document that decides whether bulk mail reaches Gmail. Read it before Gmail reads it to you.
Yahoo Sender Best Practices
Yahoo and AOL requirements for email senders
Microsoft Outlook Policies
Outlook.com anti-spam policies and sender requirements
M3AAWG Best Practices
Industry best practice documents for messaging
07The pre-flight pass
Test your emails before you send. Spam scores, rendering, and pre-flight checks.
When to reach for thisOpen before the big send. Spam score, rendering across clients, link checks, and the pre-flight pass.
mail-tester.com
Send a test email and get a 0-10 spam score
Free and honest. Ten seconds to a score that catches the embarrassing mistakes before your subscribers do.
GlockApps Spam Testing
Test deliverability across Gmail, Outlook, Yahoo, and more
Mailtrap Email Testing
Sandbox for testing emails without sending to real inboxes
Postmark Spam Check
Free SpamAssassin score check for your email content
08Sharpen the judgment
Blogs, newsletters, podcasts, and communities for email deliverability professionals.
When to reach for thisOpen when you want the practitioners who do this for a living to be the ones answering your questions.
Word to the Wise
Laura Atkins on deliverability, policy, and best practices
Email Geeks Blog
Community-driven email marketing insights and tips
Postmark Blog
Deep technical posts on email delivery and infrastructure
Litmus Blog
Email design, strategy, and deliverability insights
Spam Resource
Al Iverson on deliverability, blocklists, and anti-spam
Mailgun Blog
Email sending best practices and deliverability guides
emailexpert
Industry news, vendor reviews, and conference coverage
Email Talk
Conversations about email from industry experts
Inbox Hacking
Weekly email marketing tips and deliverability advice
Forwards
Litmus podcast on email marketing strategy
Email's Not Dead
Mailgun podcast exploring email tech with practitioners
Email After Hours
Deliverability trends and expert interviews
Email Geeks Slack
The largest Slack community for email professionals
Where the industry actually talks. Half of what I know started as a thread in there.
M3AAWG
Messaging anti-abuse working group for industry collaboration
r/emailmarketing
Reddit community for email marketing discussion
ISIPP (SuretyMail)
Internet Service Providers and email best practices
Only Influencers
Private community for senior email marketing professionals
Mailop
Mailing list for mail operators on deliverability and abuse
ESPC
Email Sender and Provider Coalition for standards
This directory is curated by the Review My Emails team. If a tool belongs here, let us know.
And one upload for when you’d rather know before it does. Free to start, no card required.
Clean 1,000 addresses freeEvery specialist you could hire opens the same tools you just scrolled past. That’s not a mystery. It’s a shared toolbox. The judgment is knowing which one to open, and when.
Bookmark the page. When the bookmark isn’t enough, ask me.
Yanna-Torry Aspraki
Founder, Review My Emails
