SNI with mixed certs

Dovecot SNI is failing hard today. Server with n domains, each with a startssl certificate of its own, all certificates expired this morning. Decision: move to Letsencrypt. Firsr certificate issued and installed. Other domains in the pipeline. Dovecot server rebooted. Expected result: one domain returning the new cert, and the n-1 domains returning the expiration notification. Actual result: the domain with LE is returning startssl expired notifications. Manual check of the key and pem files is OK...