bounces
Help! I'm seeing 550-5.7.25 errors at Gmail!
Are you seeing this error message when trying to send emails to Gmail? 550-5.7.25 The IP address sending this message does not have a PTR re...
Topic
dns
best practice
Help! Domain of sender address does not resolve!
Are you trying to send email and seeing it rejected with "Domain of sender address does not resolve" or "Unresolvable RFC.532...
cool tools
Lookalike domain finder: Fun with homoglyphs and more
Here's a cool tool that a colleague at Valimail created recently, and if you care about protecting against people spoofing your emails ...
Deliverability Terms
DELIVTERMS: TTL
Today on DELIVTERMS , the series here on Spam Resource where we help decode email and deliverability terminology, we're digging into som...
att
Seeing AT&T Reverse DNS issues when sending mail?
Example SMTP Errors When sending email messages to the various AT&T consumer email domains (ameritech.net, att.net, bellsouth.net, curre...
Deliverability Terms
DELIVTERMS: PSL aka Public Suffix List
It’s time to decode another deliverability definition. PSL stands for the Public Suffix List , and it’s one of those things that a certain s...
Deliverability Terms
DELIVTERMS: DNS aka Domain Name System
DNS is the phone book or address book of the internet. You type “ www.google.com ” into a web browser. The web browser (or the computer that...
dns
Flapping DNS and what to do about it
Has this one ever happened to you? Your DNS record is there – and then it’s not. Or it’s there when you check certain DNS servers, but not ...
dmarc
Don't double up on DMARC
Here's a new oops that I've observed a few times recently! In case you didn't know already, you can't have two DMARC records...
changes
MX records changing for Microsoft-hosted domains ... eventually
If you're one of those weirdos (like me) who tracks what email providers hosts mail for what domains, you'll want to take note of th...
dns
Microsoft errors: 5.4.4 (unable to route: no mail hosts for domain)
When sending to Microsoft OLC (Outlook Consumer - i.e. hotmail.com, outlook.com, msn.com, live.com, etc.) domains, are you seeing this bounc...
dns
Everything broke last week
So much going on in the past week in the world of email deliverability. Multiple email platforms (ISPs/MBPs) and sending platforms (ESPs) ha...
dns
Wombatmail is still here for all your DNS needs
Did you know? For the past fifteen years, I've run a simple little website called Wombatmail that provides a set of DNS lookup tools. M...
bounces
Yahoo problems? Could be SOA record issues in DNS
Are you seeing this bounce message when trying to send mail to Yahoo subscribers? 451 Message temporarily deferred due to unresolvable RFC.5...
dns
Spamhaus is not blocking Gmail
A friend warned me of a scenario that could have the potential to freak people out, if misunderstood. It looks like this: This person is usi...
cool tools
Learn how DNS works with this new zine
Julia Evans aka b0rk is somebody smart that I follow on Twitter. She created this super cool tool that I've linked to on social media ...
cloudflare
Spamhaus Blocklist Changes
Speaking of Spamhaus, this just popped up in my RSS feed reader. It looks like Spamhaus is going to take a harder stance against users who ...
admin
XNND.com is 11 years old today
I've long had a little banner at the bottom of my xnnd.com DNS tools site that says "since 2008" but it looks like I'm go...
cloudflare
Cloudflare Launches 1.1.1.1 DNS Service
Cloudflare just launched their own public DNS service . To try it, simply configure your computer to use the DNS servers 1.1.1.1 and 1.0.0....
authentication
How to Optimize Your SPF Record
Steve Atkins of Word to the Wise just released a cool new tool: SPF Minimizer . Over on the Word to the Wise blog, he explains how it works ...