For POP3, since messages are not separated from attachments, please use
App settings -> network -> "load when checking mail" -> custom -> enter 30000 (this would be 30 megabytes, the largest message size that most mail services support).
Re: Outlook and it wipes everything from the server when it finishes downloading
Bad bad bad.
If I were you I'd consider switching all your mail apps including Outlook for Windows from POP3 to IMAP and I'd also turn off this "deleting everything" behavior.