MENTAL NOTE from http://moze.koze.net/?p=81
Converting SSL-certificates from CRT format to PEM
Dovecot, for example, seems to expect pem-files, while RapidSSL only issues
crt-files. The solution? Use OpenSSL to convert (via the DER-format) to pem:
openssl x509 -in input.crt -out input.der -outform DER
then
openssl x509 -in input.der -inform DER -out output.pem -outform PEM