A few years ago, I was knee-deep in a marketing tech stack migration when someone from IT pinged me: “Hey, did you update the SPF record for that new tool?”
I… had not.
Cue the frantic DNS lookup, the realization that we were one include: statement away from hitting the 10-lookup limit, and the growing suspicion that nobody actually knew if our DMARC was configured correctly. We patched it together, moved on, and I made a mental note: someone should build a simple tool for this.
That someone turned out to be me. Several years later.
I started this project ages ago, got 60% of the way there, and abandoned it like every other side project in my graveyard of half-finished ideas.
Meet SendReady
SendReady is a free email deliverability checker I built to validate the stuff that breaks email delivery: SPF, DKIM, DMARC records, and the one-click unsubscribe headers that Gmail and Yahoo now require.
Is it needed? Honestly, probably not. There are plenty of tools out there. But I built it anyway.
Why Build Something That Already Exists?
I started this project ages ago, got 60% of the way there, and abandoned it like every other side project in my graveyard of half-finished ideas. When Claude Code came along, I decided to dust it off and see what was possible. Turns out, a lot.
It also would have been useful at a previous job. Every time we added a new tool to the martech stack, someone had to manually check if we’d broken email authentication. Usually that “someone” was me, usually at 4pm on a Friday, usually after emails had already started bouncing.
And honestly? Why not. Yes, I know MXToolbox exists. And Mail-Tester. And Learndmarc. And dmarcian, EasyDMARC, DMARCLY, Google Postmaster Tools, and roughly forty-seven other options. But adding one more free tool to the internet felt like a reasonable use of my evenings. The journey was the destination, or whatever.
Why This Stuff Matters
If you send marketing emails, or really any bulk email, authentication records are table stakes now.
In February 2024, Gmail and Yahoo dropped the hammer on bulk senders: DMARC required for anyone sending more than 5,000 emails per day, one-click unsubscribe headers mandatory, and spam rate thresholds that actually get enforced. Microsoft followed suit in May 2025, starting to outright reject non-compliant emails instead of just junking them.
For most companies with a simple tech stack, this is a “set it once and forget it” situation. But if you’re managing multiple sending platforms (HubSpot, Salesforce, SendGrid, Mailchimp, that one-off transactional email service your engineering team spun up three years ago), things get complicated. Every new tool needs an include: in your SPF record. Every vendor change risks breaking DKIM. And DMARC? Most people set it to p=none and never look at it again.
SendReady won’t solve all your problems, but it’ll at least tell you if something’s broken.
What It Checks
Four things: SPF (is your record valid, are you near the 10-lookup limit), DKIM (is your signature set up correctly), DMARC (do you have a policy, is it actually enforcing anything), and email headers (are your one-click unsubscribe headers present and properly formatted).
Punch in a domain, paste in some headers, get results. Nothing is stored. When you close the tab, the data’s gone. I didn’t want to deal with the complexity or responsibility of storing user data, so I just… didn’t.
And if you’re staring at a broken SPF record at 4pm on a Friday, I hope this tool saves you a few minutes.