How to redirect all e-mail messages sent to a user using Sieve scripts?
Solution
In order to have all messages sent to a user (we will user john@example.org) redirected to a specific address (we will use doe@example.org), you must take the following steps:
1) Via Webadmin -> Security & Filtering -> Incoming Message Rules
2) Click on "Add Message Rule"
3) Type a name for this rule
4) In the "Matches" area select:
To - Contains or Matches - type the email address to match; in our case john@example.org
5) In the "Actions" area select:
Redirect To - type the email address to redirect to; in our case doe@example.org