Issues on Mail with Yosemite

after yosemite, my mails having issues with outgoing serve smtp is always offline. OK i have read some solutions here, but i tried mine by deleting the account and add in again. it works at time, so that's one .

Another issue i have thousands of emails which i did not delete for future work references and its all gone!!!!

How do i retrieve? i do not think i have any backup.

Please help me oh good people here.