Help with an accomplishment bullet

I'm working on refining my resumé, and I've been trying to figure out the best way to highlight a particular accomplishment. In my current role I'm responsible for building an internal community across a very large enterprise (tens of thousands of employees). In my region there are a total of roughly 1600 managers who would represent my client base, and I've expanded subscriptions to a regional email newsletter from around 250 (the number my predecessor had in his Outlook list) to the current total of almost 1200 - a nearly 5-fold increase. This has also improved recognition of the internal community "brand" and reputation. The method was creating a regular email newsletter, filling it with good, useful, timely content, and growing the subscription base via word-of-mouth over a six-month timeframe.

Here are some possibilities I'm considering for the bullet:

• Increased newsletter subscriptions 450% using word-of-mouth promotion.
• Improved community membership five-fold with expanded communications.
• Grew exposure for the community 450% through frequent high-quality newsletter.

I'm open to any suggestions for how to best word this - I suppose it depends on the role I'm applying for, but I'm having difficulty finding the words to get the right emphasis. Any suggestions are welcome!