I've installed LE certs on my Dovecot a while back, and, it has been
working OK since, but, today, an iPhone user said he can't get emails as
iphone says 'cert is expired', searching around, I see some other iPhone
similar issues reported, do I have my conf correct, I have;

# cat dovecot.conf | grep ssl
ssl = required
verbose_ssl = no

ssl_cert = </etc/letsencrypt/live/fqn.myserver/fullchain.pem
ssl_key = </etc/letsencrypt/live/fqn.myserver/privkey.pem

is fullchain.pem and privkey.pem is what I should be using ?

anythought how to force an iphone to reload cert ?

actual cert was renewed 15/7, old/previous one expired earlier today

ls /etc/letsencrypt/live/fqn.myserver/
cert.pem  chain.pem  fullchain.pem  privkey.pem

(if I open mailserver host in browser, padlock shows current/valid cert)