How do I limit how long emails stay on my phone?

[Jenra]

How do I limit how long emails stay on my phone?  Before the upgrade in October, I could limit how long emails stayed on my phone.  After the upgrade that limit disappeared.  I now have over 600 emails on my phone and no way to get rid of them all.  As soon as I delete, say, 50 messages, the phone downloads another 50 from weeks ago.  All these emails have slowed down my phone.  How do I get rid of them???