Why is there no PLAIN authentication option?

I work for a company that requires the option for PLAIN authentication with their IMAP service.

emClient is the only email client that does not work with their set-up. Thunderbird, Outlook, every Android client I’ve tested all work fine. Why is this simply option not part of emClient?

There are a number of my company’s customers who could be talked into purchasing a license for this but this missing option makes it a no-go.

I’ve looked through over forum support posts here asking the same question with no resolution. There was one post where a support team member said it was put forward as an idea - but that was 3 years ago (seriously).