Free tool
Send a message and see whether it reaches the inbox: authentication, reputation, content and a score from 0 to 10.
Test address
@mailtester.hostsuar.com
Reference
We start at 10 and each thing that fails subtracts the amount shown next to it. Whatever we couldn't check doesn't subtract: we just tell you.
Authentication
We don't just check whether your records exist. We evaluate SPF for the IP that sent it, verify the DKIM signature against the key you publish and check that DMARC aligns with the From your recipient sees.
What the recipient sees
examplespf=pass
203.0.113.10 authorised on tudominio.es
dkim=pass
d=tudominio.es · rsa-sha256 · 2048 bits
dmarc=pass
DKIM aligned with the From
spf=softfail
if you send from an IP that isn't listed
The score
The table is the same for everyone and each row of the report says how much it subtracts. Serious issues, such as DMARC failing with your policy active or being on Spamhaus, weigh much more than a formatting detail.
A sample report
exampleSPF softfail
the IP isn't in the SPF
No reverse DNS
the IP has no PTR
SpamAssassin 2.1
each point subtracts 0.6
From without a name
just the address
The test
Send from the same account, application or platform you use with your customers, with the same sender and template: if you change the path, the report is about a different email. Fix one thing at a time and repeat with a new address.
A test that's useful
Same sender
the From your customers see
Same path
your usual account, SMTP or platform
Real content
the template, the links and the images
No private data
no conversations with customers
One change at a time
and a new address to repeat
It's an address that receives a message from you and analyses it the way your recipient's server would: whether SPF authorises the IP that sent it, whether the DKIM signature is valid, whether DMARC passes with the From domain, whether that IP is on any blacklist, what score SpamAssassin gives it and whether the message is well formed. It helps you find out why your emails end up in spam, or check that a new account or application sends correctly before using it with customers.
Not necessarily. The score sums up what can be checked from outside: authentication, IP reputation, content and format. Gmail, Outlook and the rest add what only they can see: how your recipients react (whether they open, delete or mark as spam), your domain's history and their own filters. A high score rules out technical faults; if you still land in spam with a 10, check the message headers in the recipient's mailbox.
We analyse it and delete the original as soon as the report is ready. The report (sender, subject, technical data and results) is kept for seven days at a link only the person with the address knows, and is then deleted. Even so, don't send private data: use a template or a test message with the real format, not a conversation with a customer.
Because DMARC doesn't only ask whether they pass, but whose they are. SPF is checked against the Return-Path domain (where bounces go back to) and DKIM against the signing domain (d=). If neither is the From domain your recipient sees, DMARC fails. It happens a lot with newsletter platforms, which sign with their own domain: set up your sending domain in them so they sign with yours, and check it with the DMARC checker.
Ten addresses per hour. Each address waits thirty minutes and accepts a single message: to check a change, generate another and repeat. If you've changed your DNS, wait until the change has reached everywhere (you can see it in DNS propagation) before testing again.
