I'll try to explain my thoughts even though I'm still working them out in my mind.
I left college after 3 years and haven't graduated (yet... I'm going back for the first time in 13 years next month). It was my understanding that a woman in my sorority is not considered an alumna unless she graduated. I've spent the past 13 years figuring I was in some sort of limbo... not an active, not an alumna... not valued by the sorority.
I always envied my husband (though he did graduate) because their slogan is "Once a Sig, always a Sig". He gets a newsletter that we both enjoy reading and we've contributed financially... but he has yet to get involved in an alumni group. He's thinking about it, though.
When I began making plans to go back to school (at a different university... one that doesn't have an AXO chapter, unfortunately) I started thinking back on my Greek days. Sadly, I've lost touch with my sisters but I'd like to get involved in supporting my sorority in some way. When I visited the AXO web site I am listed in the directory under "alumnae" so maybe I am one after all.
I guess I'm one of the unusual ones who is finding her way back just out of affection for the group as a whole... not because of loyalty to my particular chapter or because of having a group of sister friends. I just found out that my chapter (at the University of Cincinnati) no longer exists and I have no idea why. I'm surprised at how much that news deeply saddens me.
I think the best way to promote alumni involvement is to maintain communication with the members. Of course, that's easier sad than done if you don't have a current address.
Best of luck to all of you.