Mail-Tester vs Content Analysis Tools
Different tools solve different problems. Here's when to use technical testing tools like Mail-Tester versus content analysis tools like Sendable.
Email deliverability depends on two things: technical setup and content quality. Most people know about technical testing tools like Mail-Tester, but content analysis is equally important—and often overlooked.
TL;DR
Mail-Tester checks your technical setup (SPF, DKIM, server config) after you send. Content analysis tools check your email copy for spam triggers before you send. You need both for maximum deliverability.
Understanding the Two Types of Testing
Technical Testing Tools (Mail-Tester, GlockApps)
These tools analyze your email's technical infrastructure:
- SPF, DKIM, DMARC records – Is your email authenticated properly?
- Server configuration – Is your sending server configured correctly?
- Blacklist checks – Is your IP or domain on spam blacklists?
- Inbox placement – Where does your email actually land?
The process: You send an actual email to a test address, then get a report.
Content Analysis Tools (Sendable, SpamAssassin)
These tools analyze your email's content:
- Spam trigger words – Are you using words that trigger filters?
- AI detection – Does your email sound robotic or generated?
- Sales pressure – Is your copy too aggressive?
- Language patterns – Are you using spam-associated phrases?
The process: You paste your email text and get instant feedback.
Head-to-Head Comparison
| Feature | Mail-Tester | Sendable |
|---|---|---|
| What it checks | Technical setup | Email content |
| When to use | After sending test email | Before sending any email |
| How often to use | Once after setup changes | Every email campaign |
| Price | 3 free/day, then paid | Unlimited free |
| Signup required | No | No |
| Speed | Minutes (send + analyze) | Instant (paste + check) |
| SPF/DKIM check | ✓ | — |
| Spam word detection | Basic | 1000+ words |
| AI phrase detection | — | ✓ |
| Blacklist check | ✓ | — |
When to Use Each Tool
Use Mail-Tester When...
- Setting up a new email domain
- Changing email service providers
- Troubleshooting sudden deliverability drops
- Verifying your technical configuration
- Checking if you're on any blacklists
Use Content Analysis (Sendable) When...
- Writing any new email campaign
- Crafting cold outreach emails
- A/B testing different copy approaches
- Training team members on good email writing
- Troubleshooting low open rates
💡 Best Practice: Use Both
For maximum deliverability, use Mail-Tester once to verify technical setup, then use Sendable for every email you write.
Think of it like a car: Mail-Tester checks if your engine is working (do once), Sendable checks if you're driving correctly (do always).
Why Content Analysis Matters More Than You Think
Most marketers focus heavily on technical setup but ignore content analysis. Here's why that's a mistake:
- Technical setup is "set and forget." Once configured correctly, SPF and DKIM rarely change. Content changes with every email.
- Content is the #1 filter trigger. Modern spam filters use machine learning to analyze language patterns—not just technical signals.
- Recipients make decisions based on content. Even if your email reaches the inbox, spammy content gets deleted (or reported).
- AI detection is new and aggressive. In 2025, spam filters actively detect AI-generated and template-sounding language.
Complete Email Testing Workflow
Here's the ideal workflow for maximum deliverability:
Initial Setup (One-time)
Configure SPF, DKIM, DMARC → Test with Mail-Tester → Fix any issues
Write Your Email
Draft your email with your message and call-to-action
Check Content (Every Email)
Paste into Sendable → Fix flagged words → Recheck until clean
Send Test Emails
Send to your own Gmail/Outlook accounts → Verify inbox placement
Send Campaign
Confident your email will reach the inbox!
Other Tools in the Ecosystem
| Tool | Type | Best For |
|---|---|---|
| Sendable | Content Analysis | Pre-send spam word checking |
| Mail-Tester | Technical Testing | SPF/DKIM verification |
| GlockApps | Inbox Placement | Testing across multiple providers |
| Litmus | Email Preview | Visual rendering across clients |
| MxToolbox | DNS/Blacklist | Checking blacklists and DNS |
Check Your Email Content Now
Sendable's spam checker is free, instant, and doesn't require signup. Paste your email and see flagged spam triggers in seconds.
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