why am I not getting all my mail, in timely fashion?

I go on Mail, and only some of my mail shows; later, older mail shows up, or it seems overly delayed. For example, it will only show up to 1pm or so, for the new mail, checked in the [late] evening (yes, I pushed get new mail, repeatedly, and waited quite some time).

Of late, I have noticed that old mail is showing up as 'new', that was even months old, for instance in junk mail...

I'm confused. Also, yesterday I had 15k+ mails, and yet today its like 8k...??? wth?

Anyone else had this hapen, and have a fix???

thx

GT