There is.
Long press the account -> options and folders -> account options -> turn off "remove deleted messages".
And one step back from that -- at "options and folders" -- please check that the account is indeed POP3 and not IMAP.
You will also need to increase:
Aqua settings -> network -> WiFi / Mobile -> "Load when checking mail" (size)
This is so Aqua downloads each message *fully* when it checks mail -- and doesn't try to go back to server to complete the downloading later, and the message(s) not there anymore.
However, for multi-device sync (mobile, desktop, doesn't matter) -- I really, really recommend using IMAP everywhere.
With Comcast, it's something you have to sign up for (the default is POP3 only, how 1996):
https://xcsignup.comcast.net/onboardingapps/imap