When I read and/or dispose of an email on one device it continues to appear as unread in others,. Devices in question are iMac, MacBook Air, iPad mini and iPhone
What type of email account do you have (POP or IMAP) and who is the email provider, for example Verizon.
I use yahoo mail and my wife uses gmail and both have the problem
Check the settings, both of these accounts can be setup as POP, if they are they will not synchronize.
Retrieving data ...