This error indicates that there is a syntax problem with your MTA-STS Policy .TXT file hosted on your https://mta-sts.domain.com/.well-known/mta-sts.txt URL. Possible errors include:

No .TXT file found at "/.well-known/mta-sts.txt"
Required key-value pairs are missing (V, Mode, and Max_age are all required keys)
Key is present, but the value is missing or incorrect (typo or wrong value)

DMARC is the key to improving Email Deliverability!

Email is the key to your customer communication strategy. But, what is your email reputation?

Setting up and managing your DMARC configuration is the key to getting insight into your email delivery. MxToolbox is the key to understanding DMARC.

MxToolbox Delivery Center gives you:

Who is sending phishing email purporting to be from your domain
What is the reputation of your domains and delegated IPs
Where other senders are and What their reputations are
How your SPF, DKIM and DMARC setup is performing
What on-going maintenance you need to maintain and improve your email deliverability

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MTA-STS Policy Syntax Check

More Information About Mta-Sts Policy Syntax Check

DMARC is the key to improving Email Deliverability!

MxToolbox Delivery Center gives you:

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