What is Sieve?
Sieve is a scripting language that filters incoming email. When sieve is configured on a mailbox, each incoming email will be tested. If the email meets the sieve test requirements, an action will be performed.
Note that only incoming messages are tested using sieve. Outgoing messages cannot be tested.
Sieve can be used to accomplish tasks such as rejecting emails over a certain size, sending emails with certain contents to different folders, and more.
How to Add Sieve Filtering Rules to Your Mailbox
Note: Many common email configurations can be set up in the Account Control Center (ACC). We recommend only using sieve if you do not have access to the ACC.
Sieve can be added to mailboxes within compatible email clients, such as RoundCube. Visit the sieve wiki for a list of all the sieve-compatible email clients. Consult your chosen email client’s documentation for steps on how to add sieve rules.