Problem with Mountain Lion operating system

Hi All, Any advices appreciated.

I recently upgraded the operating system on my Imac to the new Mountain Lion OS. I purchased this via Apple Application store. The installation went fine, but then it started stuffing up my E-mail accounts - and eventually deleted all my historical E-mails. The new OS wouldn't recognise my mail accounts or allow me to send E-mails. I tried all the online tips with regards changing mail preferences and editing ingoing and outcoming server info and passwords and changing ports utilised. I spent endless hours on phone to internet provider, only to be told in the end that it was a Mac OS problem. In utter frustration I did a System Restore and re-installed the old operating system, which also restored the lost E-mail history.

I'm already out of pocket the $20 for Mountain Lion, but can anyone tell how you can safely install Mountain Lion so that it works with E-Mails? Has Apple released a fix for Mountain Lion?