[exim] TLS key file

When is the file specified by tls_privatekey read, in a daemon exim?
Once at startup, or every time a TLS connection is made?

IOW, does exim need to be SIGHUPed when the file changes? And does the
file need to be readable by the exim user or group id?

Thanks.

--
Please don't Cc: me privately on mailing lists and Usenet,
if you also post the followup to the list or newsgroup.
To reply privately _only_ on Usenet and on broken lists
which rewrite From, fetch the TXT record for no-use.mooo.com.