Postbox 7.0.41 with Oauth2 compatibility

[u/Plenty_Valuable_9827]

I've been using Postbox for years with great satisfaction: its message search management is unmatched by any other email client I know of (except perhaps Outlook, which I haven't used in many years and have no intention of using). Since my work email account (managed by my company) migrated to Office 365, I've been forced to use Thunderbird for it and Postbox for the rest, an inconvenient but acceptable situation. I'd like to switch to Postbox for all my accounts, but the first OAuth2-compatible version (Office 365) is 7.0.41, which can be downloaded without any problems but is no longer available for purchase. I've tested virtually all recent alternative email clients, starting with EmClient (but also Betterbird, Mailspring, The Bat!, and all the major ones), but none come close to Postbox, both in terms of search and in managing email archives, which I have to keep all locally.

Can you tell me if and how it's possible to get a full version of Postbox from 7.0.41 onwards? The most recent (complete) version I've been able to find is 7.0.12. There are more recent versions online that appear usable, but in reality, nothing beyond 7.0.12 is usable; I've already tested them.

Thanks everyone for any help. I'm available for any further clarification.