(I used to run my own cloud based e-mail aggregator www.inbox2.com)
The primary problem with these services is that they have to pull content and have to do it regularly. That means going and checking your inbox every 2-5 minutes to be able to provide a descent experience. Your ISP e-mail provider (or gmail etc) sit there and wait for e-mail to be sent to them making it less processing intensive (push based systems).
There are some techniques such as imap IDLE to make this a bit more efficient but 1. not every e-mail provider supports that and 2. for ex. with gmail idle caps at about 35K connections per box.
You could also have for ex. gmail forward all email to a custom address but average users generally found this very confusing and couldn't get this going.
We calculated that it cost us about 2 euros per month to support a free user providing a 'good' user experience. Good luck making that back as paid service is also not a (scalable) option; the general consensus being: "email is supposed to be free" or "I am already paying for my gmail!".
The primary problem with these services is that they have to pull content and have to do it regularly. That means going and checking your inbox every 2-5 minutes to be able to provide a descent experience. Your ISP e-mail provider (or gmail etc) sit there and wait for e-mail to be sent to them making it less processing intensive (push based systems).
There are some techniques such as imap IDLE to make this a bit more efficient but 1. not every e-mail provider supports that and 2. for ex. with gmail idle caps at about 35K connections per box.
You could also have for ex. gmail forward all email to a custom address but average users generally found this very confusing and couldn't get this going.
We calculated that it cost us about 2 euros per month to support a free user providing a 'good' user experience. Good luck making that back as paid service is also not a (scalable) option; the general consensus being: "email is supposed to be free" or "I am already paying for my gmail!".