Why an Email Address Is Blocked in Assurance

Below is a table of common reasons why an email address is blocked. If you receive a notification that an email is blocked, it is best to check the email address is correct first. If it is correct and you are receiving one of the reasons below, please let your IT manager know so they can investigate the issue.

Reason	Description
unknown_provider	The MX provider is an unknown provider.
no_mx / No MX host found	The recipient domain does not have a valid MX host. Note: this reason will be consolidated to only “no_mx” in the future.
high_risk_domain	Information obtained about the domain indicates it is high risk to send email to.
subdomain_mailer	The recipient domain is identified to be a subdomain and is not on our exception list. Subdomains are considered to be high risk as many spammers and malicious actors utilize them.
immature_domain	The domain is newly created based on the WHOIS information.
tld_risk	The domain has a top-level-domain (TLD) that has been identified as high risk.
mailbox_does_not_exist	The mailbox is undeliverable or does not exist.
mailbox_is_disposable_address	The mailbox has been identified to be a disposable address. Disposable address are temporary, generally one time use, addresses.
mailbox_is_role_address	The mailbox is a role based address (ex. support@…, marketing@…).
failed custom grammar check	The mailbox failed our custom ESP local-part grammar check.