Unless your emails are encrypted on your end and the receiver has decryption that matches, NO, your emails can be intercepted by thousands of people. When an email leaves your computer it also leaves your building (and your very secure data center if you have one) and goes onto the internet – it will hit your ISP (Internet Service Provider) first and then travel through a few routers and switches until it hits the recipients ISP and goes from there to the person you sent it to. All of these “boxes” are accessible by support staff BUT nobody can read a few million emails every minute. These people (support) could make copies of your emails and then read them but WHY would they?There’s a couple of reasons they would not do this: a) cost and b) loss of business if uncovered. We all know that phones can be wire-tapped and so can emails BUT to do this to all emails would be an insurmountable task. The potential loss of business would be the major hurdle, not to mention, what would the motivation be? In the end, if you have nothing to hide then this most certainly does not happen to your emails but who knows in this day and age.
Several ISP’s actually have in their client agreements that they have the right to access the text of the emails. WrapMail, the P2P (person-to-person) email marketing provider has in its agreement that they do NOT store any email text anywhere, storage is the responsibility of the sender.
Conclusion: is it possible? YES Is it probable? NO