Currently I have an HG reseller setup, that I manage for my clients. While it does come with unlimited email accounts, my concerns are 1) The webmail interface options they offer are not very attractive, and 2) I am concerned about where the data from the email boxes is stored. I'm assuming it consumes the space I allot for that particular account, and I am concerned about that eventually slowing down load times, or just hitting the space ceiling in general.
So my question is what are people using with some level of success to sell email plans? I was thining about Hosted Exchange from somewhere, but most of my clients need more basic web-based solutions, and probably would not see the value in buying Hosted Exchange. I have some clients who would, but many of my clients would probably rather just use a gmail as horrible as it is.
I am also looking into becoming a Google Apps reseller, just getting information about what others are using for Email solutions.
Every shared/reseller hosting has a limit especially when it comes to sending emails per hour. If you do not send that much, then you are ok with shared/reseller hosting.
As for your security question where the data is stored, it is within your account and it will consumed your space limit. Sure, it can slow depending on the configuration of your provider. Like I said, there is always some limitation.
If you want to avoid the above risk or even have full control, then dedicated server is what I can recommend since with your own server, you can be assured that no one is sharing the resources except you.
There are many options available. ResellerClub offers affordable (but very basic) email hosting. RC is part of EIG now (or in the process of becoming part of EIG - not sure), that's something to consider as well. Enom also has solid email options for resellers, though enom packages require that the domain be registered or have dns hosting with enom.