zimbraSmtpRestrictEnvelopeFrom has nothing to do with the drop down list of what accounts you are sending from. Here is the description that is stored in LDAP:What it sounds like is you are looking more for the "Allow sending from any address" option, or adding aliases to an account to send from. If you add an alias, it should be available to be added as a persona to send from, if the option is checked to allow sending from any address then any email address can be set up as a persona. The drop down list is filled from the external accounts and personas set up on an account.If TRUE, the address for MAIL FROM in the SMTP session will always be set to the email address of the account. If FALSE, the address will be the value of the Sender or From header in the outgoing message, in that order.