Can I enable $recipient_delimiter = ‘+’ for only the virtual sql users?

$ doveconf -n # 2.2.5: /usr/local/etc/dovecot/dovecot.conf # OS: FreeBSD 9.1-RELEASE i386
auth_mechanisms = PLAIN LOGIN disable_plaintext_auth = no first_valid_uid = 89 login_log_format_elements = user=<%u> %r %m %c mail_location = maildir:~/Maildir mail_max_userip_connections = 90 managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave namespace inbox { inbox = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { auto = subscribe special_use = \Junk } mailbox NotJunk { auto = subscribe } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox Trash { special_use = \Trash } prefix = } passdb { driver = pam } passdb { args = /etc/dovecot/dovecot-sql.conf.ext driver = sql } protocols = imap sieve service auth { unix_listener /var/spool/postfix/private/auth { mode = 0666 } } service imap-login { inet_listener imaps { port = 993 ssl = yes } } ssl_cert =

My pam users all have .procmailrc, and I do not want to interfere with those.