this few months the router keeping blocking our company user outlook email all user suddenly fail to send and received the email, outlook just keep pop up the error box Task"email@example.com" receiving reported error (0X800CCCC0F) . every time I have need to reboot the router after sometime it happened again . some of day 4-5 time ,some of day its fine . its too frequently . i believe is the router blocking the port of "110" and "587" . why i do suspect its cause by the router , is because when the error pop up , we try to use our mobile data to access the internet outlook mail, is success send and received mail , and also we found some of mail we setup as other port like 995,465 or IMAP port its not effect . We try looking for the router configuration we real no Idea what was blocking the port. our company network layout is very simple, Cisco Router > Cisco management Switch > end user. and I try to configuration the single port forwarding "TCP > internal Ip address : 192.168.1.1 > external & internal port 110 . but try to using the port checker tools it show Port 110 is closed on 175.XXX.X.XX. anyone have idea for this to solve our troubled?