Free Email Deliverability Tools: SMTP, MX, and Validation

Make Sure Your Emails Actually Arrive in the Inbox

TL;DR: Emails fail silently. You hit send, assume delivery, and never know your message bounced or landed in spam. Free tools for SMTP testing, MX record lookup, email validation, and DNS checks diagnose deliverability problems before they cost you clients, sales, or opportunities. I traced a client's "nobody responds to our emails" problem to misconfigured MX records in under five minutes.

A client told me their email outreach was getting zero responses. Not low responses. Zero. They'd sent 200+ emails over two months and hadn't received a single reply.

My first instinct was to check their messaging. But the copy was fine. The problem was simpler and worse: their emails weren't arriving. A DNS migration three months earlier had broken their MX records. Every outbound email from their domain was bouncing or landing in spam.

Five minutes with the right diagnostic tools found the problem. Ten minutes of DNS edits fixed it. They'd been invisible for three months because nobody checked the plumbing.

Check Your Email Server: SMTP Test

The Online SMTP Test verifies your email server is responding, accepting connections, and authenticating correctly. It tests the actual handshake process that happens when your server sends an email.

I run this check whenever email delivery seems spotty. It answers the fundamental question: is my email server working?

Common issues it catches:

• Server not responding on port 25, 465, or 587
• Authentication failures (wrong credentials, expired certificates)
• TLS/SSL configuration problems
• Server rejecting connections from certain IP ranges

Verify Your DNS Email Configuration: MX Lookup

The MX Lookup tool shows which mail servers handle email for any domain. MX records are the DNS entries that tell the internet where to deliver email addressed to your domain.

When MX records are wrong, email delivery breaks completely. After domain migrations, hosting changes, or DNS edits, MX records are the first thing I check.

The DNS Lookup provides a broader view of all DNS records, including SPF and DKIM entries that affect email authentication. More DNS diagnostic tools in my network tools guide.

Validate Email Addresses Before Sending

The Email Validator checks whether an email address is properly formatted and associated with a deliverable mailbox. Sending to invalid addresses hurts your sender reputation, which causes future emails to land in spam.

I validate every new contact email before adding it to outreach lists. The Email Extractor pulls email addresses from text documents, and I validate the extracted list before using it. More text extraction tools in my text tools guide.

Check Your Domain Health

Domain WHOIS

The Domain WHOIS tool verifies your domain registration is active and not expired. An expired domain means all email stops. It also confirms name server configuration, which affects MX record resolution.

SSL Certificate

The SSL Checker validates your server's TLS certificate. Modern email servers require TLS encryption. An expired or misconfigured certificate can cause email delivery failures, especially to recipients with strict security policies. More on SSL in my website launch checklist.

IP Reputation

The IP Information tool shows details about your mail server's IP address. If your sending IP is flagged or on a blacklist, your emails will be blocked regardless of content quality.

Email Deliverability Checklist

When email isn't working, run through these checks in order:

1. SMTP Test → Is the server responding and authenticating?
2. MX Lookup → Are MX records pointing to the correct mail server?
3. DNS Lookup → Are SPF, DKIM, and DMARC records configured?
4. Domain WHOIS → Is the domain active and properly registered?
5. SSL Checker → Is TLS configured for encrypted email transmission?
6. Email Validator → Are recipient addresses valid and deliverable?

Most email problems reveal themselves by step 2 or 3. The remaining steps catch edge cases and subtle configuration issues.

Preparing Professional Emails

Beyond deliverability, the content and formatting of your emails matter:

• Run important emails through the Grammar Checker before sending
• Use the Readability Scorer to keep language clear and accessible
• Attach documents as optimized PDFs using PDF Compress
• Strip metadata from attachments with the Word Cleaner or PDF Redact

More on professional communication in my business tools guide.

FAQ

Why are my emails going to spam? Common causes: missing SPF/DKIM/DMARC records, sending from a new or low-reputation IP, high bounce rates from invalid addresses, or content that triggers spam filters. Check DNS records and email authentication first.

How do I set up SPF, DKIM, and DMARC? These are DNS TXT records configured through your domain registrar. Your email service provider (Google Workspace, Microsoft 365, etc.) provides the specific record values. The DNS Lookup tool verifies they're correctly configured after setup.

Can I check someone else's email deliverability? You can check their MX records, DNS configuration, and domain status using the same tools. You can't test their SMTP server authentication without credentials, but the public DNS records reveal most configuration issues.

How often should I check email configuration? After any DNS change, domain renewal, server migration, or when deliverability seems to decline. For stability, a monthly MX and DNS check prevents surprises.

What's the difference between SPF, DKIM, and DMARC? SPF specifies which servers can send email for your domain. DKIM adds a cryptographic signature to verify message integrity. DMARC tells receiving servers what to do with emails that fail SPF or DKIM checks. All three work together.