[RndTbl] email-receive blacklist?

Trevor Cordes trevor at tecnopolis.ca
Thu Apr 29 09:16:10 CDT 2021

On 2021-04-28 Colin Stanners wrote:
> It's putting the horse before the cart to look into blocklists etc
> before the e-mail domain is correctly configured...

Thanks for the tool links!  I had thought about DNS issues.  But
literally no other host that I know of is having problems with me.

> Doing resolver lookup for T=MX domain=``tecnopolis.ca'' Questionable:
> NO MX DATA: domain=``tecnopolis.ca'' We SIMULATE! Do have at least
> one MX entry added!

Ya, this is a non-error.


My box is just my box, it's the only external-facing box, and as such
does not require a MX.  However, if some pathologically stupid MTA
doesn't know the RFC then I guess I'll setup a MX.

> https://mxtoolbox.com/emailhealth/tecnopolis.ca/
> 7 Problems
> Category Host Result
> dmarc tecnopolis.ca No DMARC Record found
> spf tecnopolis.ca No SPF Record found

This tool also sort of aggressive with its warnings.  Kind of like
SSL-setup tools moan about using invalid hashes, though 1-3% of the
hits out there are on old browsers that require them.

I don't have dmarc and spf on purpose.  Surely no MTA would that
braindead to refuse to *send* to such a server?

> dns tecnopolis.ca SOA Serial Number Format is Invalid

Can a dns client even get the SOA serial?  How does it do that?  Mine
is set to a normal int within the expected range.  Weird... I'll need
to verify my server is actually spitting an invalid value out, once I
figure out how mxtoolbox is reading that info and what value it saw.

> dns tecnopolis.ca SOA Expire Value out of recommended range

Another non-error.  My TTL is 1 week and mxtoolbox thinks it should be
min 2 weeks.

So useful tools taken with many grains of salt (as are most), at least
it gives me some ideas and I'll implement one by one and then see if
Hilton can reach me.


More information about the Roundtable mailing list