
In the Set OpenPGP Rules for field you must enter the recipient email address you're writing the rule for. Recipients are the addresses specified in the fields To:, Cc:, and Bcc: of the email message, without distinction. If you want to have a rule for multiple email addresses, enter them all in the field, separated by spaces. Then choose the pattern matching criteria from the drop-down menu (Is exactly, Contains, Starts with, Ends with).
In the Action zone you specify the Enigmail behaviour if there is a match with the specified recipient email address(es):
In the Defaults for... zone you decide whether to activate signing, encryption and PGP/MIME if the rule is matched. Each function can be independently set to three options:
When sending a message to multiple recipients, in case of conflicts between rules, Never overrules Always. For instance, if you created two rules for the following two recipients:
alice@example.com
Signing: Always
Encryption: Always
PGP/MIME: Yes, if selected in Message Composition
bob@domain.org
Signing: Always
Encryption: Never
PGP/MIME: Never
and you try to send a signed and encrypted message to alice@example.com and bob@domain.org, the message will be signed only. Also, should you have turned on PGP/MIME when composing the message, this setting would have been ignored and the message won't be encrypted with PGP/MIME.