[CentOS] Yum - which repo did a package come from

guys,

i have installed mailscanner, spamassassin, etc on my machine. This was done sometime ago. Some of these rpms i got not frm centos repos.

What command ( or yum command )  can i  use to find out which repo did this installled package come from.

yum info packagename just says; 

repo : installed

i was hoping for something like repo:rpmforge or   something similiar. i have these 3 rpms which i cant remember where i got them from.


dovecot-1.0.7-7.el5             
mailscanner-4.74.13-2          
spamassassin-3.2.5-1.el5

Regards,
Marco.