In case that you are demanded to keep the jar library as small as possible, you can include the SMTP/POP3/IMAP function separately to avoid the "too many methods in the dex" problem.
You can choose the wanted jar libraries from the javanet web page, for example, mailapi.jar + imap.jar can enable you to access icloud, hotmail mail server in IMAP protocol. (with the help of additional.jar and activation.jar)