[exim] DKIM Certificate Issues

Hi,

I have configured Exim 4.92 to sign out going emails with a DKIM certificate but I always get errors:

2020-02-16 03:45:10 1j3FY3-0005tu-Vh signing_init: privkey PEM-block import: error:0909006C:PEM routines:get_name:no start line
2020-02-16 03:45:10 1j3FY3-0005tu-Vh DKIM: signing failed: PRIVKEY

This seems to indicate an issue with the format of the private key but it was generated with openssl following the instructions in the Exim documentation. I have made sure that Exim has ownership of the files and read access.

Any suggestions.

Thanks

Neal