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Show HN: DMARC Checker

dmarcchecker.app

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Re: Show HN: DMARC Checker

#2

Post by akshayKMR »

Hey, this comes at a perfect time for me.

I had posted my app on Betalist about a week ago and received a vulnerability report about incorrectly configured DMARC from a security researcher. I made the fix but wasn't confident about it. Shortly after, I received a couple more similar emails.

With this tool, my first check failed, citing an invalid SPF record. (I had an extra `.` at the end of my TXT record). Now, the check shows all passing.

I hope all is good now (emails are wild).

From my limited understanding:

    SPF
Thanks!

Re: Show HN: DMARC Checker

#3

Post by awulf »

akshayKMR wrote: post #2

Hey, this comes at a perfect time for me. I had posted my app on Betalist about a week ago and received a vulnerability report about incorrectly configured DMARC from a security researcher. I made the fix but wasn't confident about it. Shortly after, I received a couple more similar emails. With this tool, my first check failed, citing an invalid SPF record. (I had an extra `.` at the end of my TXT record). Now, the…

I'm really happy to read that the app was able to help! Thanks for sharing.

Re: Show HN: DMARC Checker

#5

Post by RulerOf »

This is a really straightforward tool. Validating spf/dkim/dmarc by receiving an email strikes me as more effective than something that just looks at the DNS records. Thanks for sharing.

Re: Show HN: DMARC Checker

#6

Post by aeadio »

A simple reject policy is showing up as an error, despite validating fine with other DMARC checker apps like MX Toolbox,

    The From domain (...) has an invalid DMARC record.
    ...
    DMARC record found: v=DMARC1; p=reject;
    The DMARC check result is permerror.
No explanation as to what permerror means.

It might also be useful if the tool attempted to circumvent DNS caching, so users can try tests in succession after updating.

Re: Show HN: DMARC Checker

#7

Post by petecog »

petecog wrote: post #4

I've given it a go. I recommend also https://mxtoolbox.com/dmarc.aspx I have no affiliation.

Great tool. Good comprehensive report. Keep up the great work. Hope it helps people.

Email is such an amazing mess. Love and hate in equal measures

Re: Show HN: DMARC Checker

#8

Post by awulf »

aeadio wrote: post #6

A simple reject policy is showing up as an error, despite validating fine with other DMARC checker apps like MX Toolbox, The From domain (...) has an invalid DMARC record. ... DMARC record found: v=DMARC1; p=reject; The DMARC check result is permerror. No explanation as to what permerror means. It might also be useful if the tool attempted to circumvent DNS caching, so users can try tests in succession after updating…

There was a small bug in our DMARC record parser (it didn't like the semicolon at the end of the record). Sorry for that. Your DMARC record is definitely correct. The issue should be fixed now.

Also, thanks for the idea about circumventing DNS caching. I'll look into adding that feature.

Re: Show HN: DMARC Checker

#9

Post by jenoer »

I don’t want to take away your spotlight, because it’s a nice project you launched,

But I do want to point out to people that https://github.com/domainaware/checkdmarc exists for quite a while. I use it often and have also integrated it in various automated tooling.

(It also does not require handing out email addresses to strangers.)

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