You use the imap mail protocol. IMAP When an email program uses the IMAP protocol, messages are stored both on the mail server and on the local device where the email program is running. Changes are synchronized between the client and the server. Therefore, if you access your account from more than one device, you see the same set of messages, message status and folder structure regardless of the device you are using (because all the email programs synchronize with the server). The main drawback of IMAP is that it tends to send and receive more traffic between the device and the mail server, so performance can be poor if your internet connection is slow or costly if you are paying expensive rates for data use (for example, on a per-megabyte basis). Accounts that use the IMAP protocol may confuse people if they are not aware of the synchronization aspect. A person might think that deleting a message on one device only deleted the local copy, not realizing that the message is also deleted from the server and therefore all other devices that access that account.