With Shiftserver you are able to have unlimited email addresses with your account. The only space limit is the total storage space limit of your account.
By default, cPanel sets new accounts with 250MB of mailbox space, but this can be adjusted up or down as you like from the Email Accounts section in cPanel. You can even set your email accounts to "unlimited" if you like.
There is a 200 outgoing email hourly limit per domain. This limit is also applied towards Mailman. If you send over this amount in any hour, most of the e-mails will bounce back with an undeliverable error. If this occurs, it will then take some time for your account to be able to send again so we recommend waiting at least 1 hour after this issue occurs to begin sending email again.
NOTE: There is a 10MB limit on sending and receiving email attachments (files attached to an email).