downgrade

this may sound odd, but I want to downgrade a package (dovecot)

I have Leap 15 installed, but also have the DVD’s of Leap 42.1, 42.2 and 42.3
An older version must be on these - but how do I get at it?

Best regards, WalterU

I wouldn;t take one from previous releases, but rather seatch https://software.opensuse.org , you might find users building older releases for 15. Or … you can use your credentials and start using OBS. You setup a Leap 15 repo, branch and older version of dovecot, let it build for 15 and see what happens ? Done that.