I am curious to know what other businesses do to communicate with their owner clients. Do you send out newsletters? How often do you send these? Do you send Christmas cards (its getting pretty pricey!) ? Any other good ideas?
We do a quarterly newsletter via Mailchimp and try to stick to a template - local rental stats, office news, maintenance or other tips.
We do monthly landlord and tenant newsletters and a quarterly tradie newsletter as well.
We try to keep our facebook up to date with information as well and encourage clients to follow us there. We give small gifts of a Xmas basket to our larger clients as well. 
We send out monthly newsletters to our owners which seem to be well received to keep them updated with our business and any legislation changes but also include any properties for sale that they might be interested in adding to their portfolio. As we are a smaller office, we aim to call all our owners after routines to touch base and I make random calls to also stay in touch.
We use MailChimp for our newsletters and find it really easy to use
We try not to overload our owners with information and only send out newsletters when we have important information or happy information to share