Re: letters keep coming back
This is not a bug with the phone but with the providers, who are not prepared to deal with a problem that is massive and which requires a reworking of standards.
If your email is set up as an IMAP account, if you delete an email from any device, it removes it from the server. If your email is set up as a POP account, deleting a message only deletes it locally. This works great through an email client on your computer, but with smartphones, which access mail servers in a different way, the server is not understanding that the email on your phone has been read and deleted. It stupidly thinks it was never sent to your phone, so it dutifully sends it again.
I prefer POP because there are a lot of email messages that I want to keep on my computer but not on my phone. A ehile back I followed a procedure on my iPhone that successfully sorted this problem out but I managed to forget how I did it.
In a separate issue, I ended up having trouble using AT&T's outbound server so I did what used to work properly – I deleted the email account from my phone, along with the server presets, then added the email account back. Somehow I managed to lose a magic setting and I'm back to dealing with a couple hundred messages that keep redownloading.
If I stumble across the fix, I'll post it here. One thing I will do (and others can check this out as well) is to access my email account via a web browser and see if there is a setting there that will take care of the downloading issue.
In the meantime, the only way I know is to switch your email to an IMAP account and being careful about which messages you delete, and moving messages you want to save into a separate folder.