Debian builds Exim against GnuTLS because OpenSSL used to use a license with an advertising clause, making it incompatible with the GPLd Exim.
Since OpenSSL 3 is now available under a GPL-compatible license, I think it's long past time to switch. But judging by the sorry state of https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=446036 I don't think it's going to happen any time soon.
Since OpenSSL 3 is now available under a GPL-compatible license, I think it's long past time to switch. But judging by the sorry state of https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=446036 I don't think it's going to happen any time soon.