Message sender

This condition lets you filter messages based on who sent them. You have several ways to match the sender:

Email Address

Enter the sender's email address and choose how to match it:

Exact match – The email address must match exactly (e.g. john@mshsoftware.com)
Wildcards – Use * to match patterns (e.g., *@mshsoftware.com matches anyone from that domain)
Regular expression – Use advanced pattern matching for complex rules

Select user window

Select a specific user from the list.

The condition will match if that user is the sender.

Select group window

Choose a group from the list. The condition will match if the sender belongs to that group.

This is useful when you want to apply the same rule to multiple users at once.

Select domain window

Select a domain. The condition will match if the sender's email address belongs to that domain.

This makes it easy to handle all messages from a specific organization or mail server.

Domains - read more about Domains settings
User attributes - read more about Users and Groups
For information about regular expressions you could check regular-expressions.info or regexone.com