Need Help with verizon email account

[tmax1964]

I have a verizon email account no problem getting to it. have a few questions on how to keep emails on the phone. when I hit my verizon email app itn opens but only keeps emails for 2 days then they disappear. some emails i want to keep for a while. I know i cam save them to my sd card ad there is a file for saved emails, but how do I keep it in the email app itself. I didnt notice in settings, what to do???
Also when deleting email from phone how do I get it to really delete off my email account. example. I delelte email from phone, two days later am on computer going into email and they are still there like I never saw them
Can anyone help with both of these
thanks