Dont know if this helps your situation but what you can do is sign up for a separate IMAP mailbox (with a new username) for $40 per year.
Found info about this on TPG website https://www.tpg.com.au/products_services/imap.php
Hope this helps
I already have a POP3 account and wish to have the same user email address name set up as an IMAP account. Can this be done for the annual fee of $40 per annum?
By the way you should post on your plans page that IMAP accounts cost $40 per annum for each account. I would NEVER have taken up a POP3 account in the first instance with you had I known this was an issue.