Higher deliverability for opted-in lists where recipients are in fact expecting the emails can be achieved via -

1) Maintaining and Increasing IP Reputation

2) Monitoring Spam Complaints through FBLs

3) Maintaining and accurate SPF record

4) Watch Sending Patterns

For further details into each step, please review the blog article at -

http://blog.arvixe.com/how-can-i-increase-deliverability-of-my-mailing-list/

Forum Reference/Discussion: http://forum.arvixe.com/smf/pre-sale-questions/vps-an-mailing-list-for-a-7-000-member-association/new/?topicseen#new