It will appear different to different people. 1 Million will generally look bigger to most people than unlimited becuase it quantatize.
Well, if it’s about a hosting plan, I suggest you use “unlimited*”. You could make a sidenote somewhere that technical limits do apply.
When you state “1 million emails”, that is a much harder claim. When someone actually tries to make 1 million mailboxes or forwards or whatever, it’s very possible H-Sphere will not like it at all 
But when you give a hard number (even a ridiculously high one), people have a right to complain if it doesn’t work 