Sticky problems

How do I keep my sent mail messages?

[BeeDeeDubbleU]

As far as I can see I have my Sticky preferences set correctly but outgoing mail is not saved. Can anyone tell me if there is a problem with this?

[engine]

The "Place a backup copy in outbox folder?" becomes unchecked after an undetermined time. Simply check it again and all's fine, until the next time.

[BeeDeeDubbleU]

I am not seeing this option?

[tedster]

The option should be right under the window where you compose the outgoing mail, BDW.