With the migration of your email systems to an outside provider, the feeling of control you might have had with an in-house system will vanish. While you will still be in control to a certain degree, the processes will be physically moved—in some cases to providers in foreign countries.
To put it another way, no company is an island. There is often a temptation to keep as much work as possible within your own walls—it makes you feel safe and secure, as though your company would be able to survive a major global cataclysm simply because you kept all of your business processes in-house. The truth, however, is that letting the right email service into your organization will help your reliability (and survivability) rather than hurt it. Keeping things in-house is often cost-ineffective and can be a recipe for impending meltdown. Again, the key is in choosing an organization that meets your needs and makes you feel comfortable. You don’t have to work with the first outsourcing company you contact. You should feel free to keep shopping until you find one that feels like a good fit.
You can also alleviate some of the stress associated with this loss of control by ensuring that your needs will not be competing with (and losing out to) the needs and interests of other companies. Make sure that your new provider is flexible and generous in their ability and willingness to respond to any issues that may arise.