> make install clean && rehash
Shared object "libstdc++.so.6" not found, required by "mysql"
make: "/usr/ports/Mk/bsd.database.mk" line 114: warning: Couldn't read shell's output for "/usr/local/bin/mysql --version | /usr/bin/sed -e 's/.*Distrib \([0-9]\{1,2\}\)\.\([0-9]*\).*/\1\2/'"
Shared object "libstdc++.so.6" not found, required by "mysql"
Shared object "libstdc++.so.6" not found, required by "mysql"
===>  exim-mysql-4.86_1 cannot install: unknown MySQL version: .
*** Error code 1

Stop.
make: stopped in /usr/ports/mail/exim-mysql