openSUSEftw
Please do not criticise the maintenance of repos, they are well mainted to my knowledge in accordance with sme requirements.
It appears to be a problem of your own creating, or should I say misunderstanding.
You probably need to configure and enable the dag repo (or wherever the required packages are maintained).
Note that sme protocol is to use the --enablerepo=reponame switch on the command line when using yum, so packages are downloaded once only from that repo.
You appear to have installed postfix, correct ?
I don't think that is recommended on sme server, and will likely break things or certainly need a lot of work to properly integrate it.
You need to enable suitable repositories that have the dependency rpms (refer above comments).
PLEASE read the FAQs and other info about how to correctly use sme server and change configuration at the command line, and get to understand yum. It is different to other Linux distros, and you cannot just go changing config files directly.
See all the links at the top of the forums page.
In particular, for starters, see
http://wiki.contribs.org/SME_Server:Documentation:FAQ#Yum_Updatesand
http://wiki.contribs.org/Category:Yum_Repositoryand
http://wiki.contribs.org/Template_Tutorialand many more.
I should also add to read up on the db commands concept, unique to sme server AFAIK.
Start here
http://wiki.contribs.org/Db_command_tutorialand
http://wiki.contribs.org/DB_Variables_Configurationand not limited to the commands mentioned therin.
See the template fragment code for ALL possibilities.
For a deeper understanding see
http://wiki.contribs.org/SME_Server:Documentation:Developers_Manual