[exim] CNAME smarthost certificate name verification

Hello list.

Exim doesn't compare CNAME with certificate names, for example

smtp.mail.yahoo.com
smtp.outlook.com

It compares A/AAAA hostnames with certificate names
With OpenSSL: SSL verify error: certificate name mismatch
With GnuTLS: TLS certificate verification failed: cert name mismatch

Is it a bug that Exim not compare CNAME with certificate names?