this night i got called because the server didnt deliver mails.
after some investigating i found following error in gateway.log:
Tue May 15 00:31:01 2018: [notice ]  Starting worker process for IMAP request Tue May 15 00:31:01 2018: [error ] [ 9209] ECChannel::HrEnableTLS(): invalid parameters Tue May 15 00:31:01 2018: [error ] [ 9209] Error switching to SSL in STARTTLS Tue May 15 00:31:01 2018: [notice ] [ 9209] Disconnecting client.
after this time no one got mails, but dagent sends everything to inboxes (no error there)
i’ve found and old ticket, but this wasnt apply here.
# enable/disable POP3, and POP3 listen port pop3_enable = no pop3_port = 110 # enable/disable Secure POP3, and Secure POP3 listen port pop3s_enable = no pop3s_port = 995 # enable/disable IMAP, and IMAP listen port imap_enable = yes imap_port = 143 # enable/disable Secure IMAP, and Secure IMAP listen port imaps_enable = no imaps_port = 993
at 04:00 the gateway service has a scheduled restart, after that everything worked again.