Macmail - could not load internet accounts preference panes

Hi,

Having a problem with MacMail on MacBookPro with operating sytem El Capitan

I can open MacMail - but it takes forever. Have tried myriad fixes but none have solved this.

1. It will not allow me to set up .pop anymore it keeps changing it to .imap.

2. The preference pane for internet accounts, sharing and extensions cannot be loaded

3. no folder, no library / preferences no .plist files for mail exist that I can see.

Anyone have any idea what is going on.

If MacMail is corrupt can it be installed again without installing the whole OS package.

Thank you