On 11.08.17 00:00, Davide Perini wrote:
> I'm pretty sure that the problem resides in your postfix/dovecot
> configuration, if you use those.
Sorry, but no. As I stated in my OP, other clients can access Dovecot
and Postfix just fine (tested with iOS Mail, Apple Mail, Thunderbird on
macOS and Windows). Roundcube 1.3 with PHP 5.6 is the only combination
causing problems, and since Roundcube uses PHP to establish IMAP
connections and I can connect fine if I disable PHP peer verification,
the cause is definitely that verification mechanism failing on my
Roundcube server. The crux is to figure out why it fails.
Google confirms that other people experienced similar problems after
updating to PHP 5.6, which enabled peer verification as a default
setting (see http://php.net/manual/en/migration56.openssl.php).
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