I need to find the setting on the email client setup for my Trophy not to delete email from the server. This is like my fifth smart phone (all windows devices), but it's the first not to have advanced options that state do not delete email from the server. I have selected the option to Leave email on the server, but I've noticed that if I delete an email from the list on the phone on subsequent syncs the those emails are deleted from the server. This can setup a situation where emails are permanently lost because they were deleted by the phone before my home client was able to download them.
The obvious easy answer is to not delete them on the phone until you confirm they have been downloaded to your home computer.
Most smartphones are set to mirror what is on the email server and vice-versa, so if you delete it on one, it is then deleted on the other.
One way to get around this would be to switch to pop mail and have a copy left on the server after downloading. With pop mail, though, you will not get instantaneous(push) notification of an incoming email. You will have to set a time interval when your phone will have to check to see if any new emails are available.