Hi!

If you search classcentral.com, you can find (free, good quality) business communications courses on lots of subjects.  That site is an aggregator for all the MOOCs.  Here are three that are coming up soon, generally related to business communications. 

https://www.class-central.com/mooc/3922/edx-ewa1-1-1x-english-at-work-in-asia-job-applications-cvs-and-cover-letters

Hong Kong Polytechnic -- starting in October 2015

https://www.class-central.com/mooc/766/coursera-crafting-an-effective-writer-tools-of-the-trade-fundamental-english-writing

This course has ran a few times.  It's pretty popular.  This latest one starts in two days; on Sept 4, 2015

https://www.class-central.com/mooc/2724/coursera-high-impact-business-writing

This one is self-paced so you do it on your own.

This is a useful page of greeting, closings (formal and less formal): http://learningwell2012.blogspot.ca/2013/01/blog-post.html