How can I get mailboxes settings from iPad to iPhone?
My first thought was that maybe you could use iTunes to sync your Mail settings back to your Mac. Then I found this: http://support.apple.com/kb/HT1296


  Mail account settings (email address, display name, server name, and user name) are synced from the computer to the iOS device; iTunes does not sync settings from the iOS device back to the computer and does not sync any email messages.


So considering this, I think your best option is to configure your complex Mail Settings on your Mac by hand first. Then, you could use iTunes to automatically sync those settings to all your iOS devices. Not a 100% solution for your problem, but I think it's the best you can do within the limitations you have.