I'm having the same problem with Bat 7.4.16 on HostXNow. Has this not been fixed in the latest version?
LOG:
SECURE TO REGULAR PORT (STARTTLS)
26-05-2018, 10:49:42: IMAP - Connecting to IMAP server mail.xxx.net on port 993
!26-05-2018, 10:50:12: IMAP - 10053 An established connection was aborted by the software in your host machine
26-05-2018, 10:50:18: IMAP - Disconnected
26-05-2018, 10:51:20: IMAP - Connecting to IMAP server mail.xxx.net on port 993
!26-05-2018, 10:51:50: IMAP - 10053 An established connection was aborted by the software in your host machine
26-05-2018, 10:51:55: IMAP - Disconnected
SECURE TO DEDICATED PORT (TLS)
26-05-2018, 10:54:30: IMAP - Connecting to IMAP server mail.xxx.net on port 993
26-05-2018, 10:54:30: IMAP - Initiating TLS handshake
!26-05-2018, 10:54:30: IMAP - TLS handshake failure. An existing connection was forcibly closed by the remote host
26-05-2018, 10:54:57: IMAP - Connecting to IMAP server mail.xxx.net on port 993
26-05-2018, 10:54:57: IMAP - Initiating TLS handshake
!26-05-2018, 10:54:57: IMAP - TLS handshake failure. An existing connection was forcibly closed by the remote host