By default, email software applications (e.g., Outlook, Thunderbird, Apple) store your sent, draft, and trash email on your computer, rather than storing it on the email server (as it should with an IMAP connection). You may need to make some adjustments to your email software setup so that sent, drafts, and trash email will be stored in your online Sent, Drafts, and Trash folders.
When you start using your new email through us with IMAP, it is important that you add a new mail account! (rather than editing your current settings). Only by creating a new account you ensure that you do not loose your mail history.
For detailed instructions per application / device, check: https://help.emailsrvr.com