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',
(if I open mailserver host in browser, padlock shows current/valid cert)
Usually, a browser connects to a web server on port 443, while an email client connects to an IMAP or POP server on a different port, served by different software. Just because your browser receives a current/valid cert, that doesn’t mean your dovecot server is sending the same certificate.
Assuming the
sbt.net.au in your email address is the address of your dovecot server, I tried
And received a cert which includes:
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
03:5b:41:a6:f4:a6:33:eb:5b:ac:af:b8:20:96:f4:0e:20:b9
Signature Algorithm: sha256WithRSAEncryption
Issuer: C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
Validity
Not Before: Apr 23 11:11:28 2018 GMT
Not After : Jul 22 11:11:28 2018 GMT
Dovecot is sending an expired cert. Pascai is correct; you need to restart it.