Maintaining a conference advertisement list
Most hosting providers offer mailing list management facilities as part of the hosting.  For example, Dreamhost, which I use for hosting my personal domain (mekki.ca), provides announcement &amp; discussion lists that can be configured with granular permissions such that multiple people can administer them.  They will be associated with the domain in question.  

As such, it's usually attached to the conference website (most hosting providers provide something similar, so contact the hosting provider of your conference's website for details).  Since you are already paying for the domain name and hosting of the conference website, there are usually no additional fees for the list management, and anyone who could access the conference website should be able to receive the list emails as well (i.e., China, etc.).

(Full disclosure: The first Dreamhost link is a referral link.  If you sign up for services, I get a small credit.)