をいじってこんな感じにするといい
#%PAM-1.0
@include common-auth
account required pam_succeed_if.so user = hogeuser
@include common-account
@include common-session
参考リンク
http://wiki2.dovecot.org/Authentication/RestrictAccess
#%PAM-1.0
@include common-auth
account required pam_succeed_if.so user = hogeuser
@include common-account
@include common-session