Same here in Debian stable - just upgraded from stable stretch to the new stable buster and broke production fetchmail system.
client Sep 15 18:14:01 boark fetchmail[4250]: OpenSSL berichtete: error:141A318A:SSL routines:tls_process_ske_dhe:dh key too small server Sep 15 18:18:01 example.com dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=10.0.0.1, lip=192.168.1.1., TLS handshaking: SSL_accept() failed: error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure: SSL alert number 40 Please escalate this bug.
