What tools measure content and header compliance?
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You've written your email, set up your authentication, and now you're paranoid. Did you miss something in the headers? Is your content going to trip a filter? Before you hit send to your list, there are free tools that'll catch most of the obvious mistakes.
Mail-Tester is the standard. You send a test email to a unique address they give you, and they score your email on spam likelihood, check your SPF and DKIM setup, and flag any content that looks sketchy. The score doesn't guarantee inbox placement, but it'll catch obvious problems. The most important part of a Mail-Tester report is the authentication section. If that's not passing, nothing else matters.
MXToolbox lets you check your domain's authentication records directly. You paste in your domain, and it shows you your SPF record, DKIM keys, and DMARC policy. It also checks if your IP is on any major blocklists.
Litmus and Email on Acid show you how your email renders in different clients (Gmail, Outlook, Apple Mail, etc.). They're not compliance checkers per se, but if your HTML is broken, it affects how filters see you. They'll flag structural problems that could cause issues downstream.
For DMARC policy monitoring, providers like dmarcian parse your DMARC reports and show you who's sending email from your domain (legitimate senders and spoofers). If you're serious about compliance, this is worth the investment.
The next step: start with Mail-Tester on your next batch. If your spam score is above 5, dig into what it's flagging. Then check your domain on MXToolbox. Once those are green, you've cleared the easy stuff.
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