Customers are the reason why all businesses exist .. So they are essential, important and powerful...and we should all love them and appreciate their loyalty!
You could send an email thank you, but the old fashioned way has far more impact. A little 'thank you' gift and a note, handwritten if possible, to your clients, will convey appreciation and definitely not go unnoticed.
June is a particularly great time to think about your clients and say 'thanks'. Everyone is focused on performance and reviewing their past 12 months of the financial year (including their supplier relationships). and it is well away from the festive 'silly season'.