[exim] extract email from tls_peerdn ?

Hello,

Using Exim 4.75, I am looking for the best method to extract the
emailAddress field from tls_peerdn variable.

For example, with my certificate, the SSL peer debug shows:
/C=FR/ST=Ille-et-Vilaine/O=Home/OU=Computing/CN=Nicolas KOWALSKI/emailAddress=niko@???

I currently extract the emailAddress using a double extract, first by
choosing the last field (separated by /), then a simple extract using
emailAddress as key.

${extract{emailAddress}{${extract{-1}{/}{${tls_peerdn}}}}}

Obviously, this will fail if the /-separated last field is not the
emailAddress.

Thanks,
--
Nicolas