The Global Email Rules is for the administrator to further refine their email traffic. It is applicable on the incoming email sender's email address.

1. You have to login as an Avomaster/VOadmin in order manage these mail rules.
2. Referring to the image below, go to (1)Profile (icon on the top section) → (2)Admin (rightmost icon) → (3)Global Email Rules (left side under Admin Task) → (4)Make any important edits on this section → (5)Update button to save the edits.

• Each line is a rule. A rule may contains wild card like those used by the Bourne shell.
  
• Each rule is prefix with an action, like this: [action] [space] [rule] [cr]

The following will allow all email from yahoo.com to get pass:

 pass *@yahoo.com

Note that the “*” sign is very important here.

The following will mark all emails from somedomain.com as Junk:

 junk *@somedomain.com

The following will reject (stop delivery) incoming mails from an email address.

 block someone@somedomain.com

The following will reject (stop delivery) of all email coming from hotmail domain.

 block *@hotmail.*

Note that the * at the end will basically block all hotmail domain including:
hotmail.com, hotmail.net or hotmail.cc

The following will reject (stop delivery) incoming mails from the domain xyz.com, including its subdomain (like shop.xyz.com, alert.xyz.com):

 block *.xyz.com

The following will allow one person vip@domain.com to pass the rule:

 pass vip@domain.com
 junk *@domain.com

This would basically block all other email from domain.com other than vip@domain.com.
However, pay attention that the pass rule must place before the junk (or reject) rule, or else it will not work this way.

Action tags available:
pass Let the email pass. The Junk ranking will set to 0.
reject (or block) Reject the email, not going into the delivery system.
junk Deliver the email, with Junk rank set as 5 at least.

Mail rules take priority over junk ranking and spam filtering system. So if an email passed the rules, it will not be scanned and tagged with junk ranking.