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Question

Can I allowlist or blocklist individual users via email addresses in the Host Access Table (HAT)?

Answer

No, you cannot allowlist or blocklist individual users via email addresses in the HAT. Actions determined at the HAT level occur before the SMTP conversation is engaged.  The remote host is not allowed to proceed to the point where they can issue 'mail from' or 'rcpt to' commands.

The HAT is driven by Sender Groups.  Sender Groups allow the following formats for adding 'senders':

- IPv6 addresses such as 2001:420:80:1::5

- IPv6 subnets such as 2001:db8::/32

- IPv4 addresses such as 10.1.1.0

- IPv4 subnets such as 10.1.1.0/24 or 10.2.3.1

- IPv4 and IPv6 address ranges such as 10.1.1.10-20, 10.1.1-5 or 2001::2-2001::10.

- Hostnames such as example.com.

- Partial hostnames such as .example.com.

To apply policies to individual users, you can create a unique User-Based Policy or create a message/content filter.

Related Information

- Technical Support & Documentation - Cisco Systems