The other day, I was talking with Helen Hoart, the former marketing agent for Harvard Health newsletters, and she let me in on an interesting tidbit.Helen helped Harvard Health transition from print-only newsletters to electronic PDFs. But when it came to renewals, she used a mixed-media approach.”After testing, we settled on a combination of print and online renewals even though we were serving electronic-only subscriptions,” Helen wrote in an email recently. This is a very important lesson for online subscription marketers who might be tempted to give up direct mail or postal campaigns — there’s still nothing like a tangible reminder to get people to convert, renew or remember.Helen also said that notifying subscribers when new issues where available was a crucial tactic to increase retention. “But a plan vanilla ‘your issue is online’ didn’t do the trick,” she confessed. “Instead we had to create enticing notifications.”