After upgradin OX your connection to the IMAP-Server is broken and you find a error message like:
com.openexchange.exception.OXException: SSL-0001 Categories=ERROR Message='The certificate with fingerprint ‘’ for domain ‘xyx.domain.tld’ is untrusted.
ucr set ox/cfg/imap.properties/com.openexchange.imap.ssl.protocols=""
SSLv3 TLSv1 which you might find with:
ucr get ox/cfg/imap.properties/com.openexchange.imap.ssl.protocols
This is due to a change in the security configuration of OX
(The two protocols are no longer supported by Java in this case.)