this happen for this few month and this few day keep making our company Email down all of my user can't receive the email by outlook but using web mail is received . we only found the solution is reboot the router after few min our few hours it happen again we can't keep reboot the router all the day 6-7 time.
and we found if using IMAP the email is able to received and using the POP3 with the same email account is unable receive.
We try to contact the ISP site and the mail server site every time they just restart the port or services and our mail is able receive again .
As long as they said is not their issues and we did try connect the laptop internet to mobile hotspot and email download and receive the mail smoothly.
We suspicious is router issues and when we check the log we found this error message .
We are no idea for this , anyone help on this?
I can provide more information if you are need.
From the the router we found this error .
From the outlook application we error is
