Ever since Comcast changed email system, i receive emails on imac, iphone and ipad but when I move, delete, etc., it is in sync with iphone and ipad but not imac. So I have to re-do, move emails, etc. twice. Any ideas?
On the iMac are you using Mac Mail? If so, is the account enabled in it using IMAP? If so, everything should be synced with the other devices. If you are using POP3, it won't be synced.
What you are describing doesn't make any sense unless you are referring to local folders that are not IMAP compliant. Anything you do to an email in one device should be reflected on any other device as long as they are all using a client with the account enabled with IMAP.