Me too. Will some explain what this window means and how to not see it at all?
Still having the same issue only with EM client. I had an idea that because I had installed as many as 3 e-mail clients (EM client, Mailbird, Thunderbird) to troubleshoot this issue that maybe my e-mail server (Netaddress) was rejecting log-ins because of too many attempts.
So for the 5th time I asked Netaddress support about the issue, they assured me their is no log-in limits and they are IMAP version 4 compatible, we reviewed my server settings and all is good.
The latest problem is that EM client will work fine for a few weeks then it just stops receiving e-mail then 5-8 days later it starts working again, Netaddress support checked their server logs and advised me that their was no rejected log-in attempts and I had the correct IMAP ports.
During this time I changed my ISP, this did not effect anything, last January I re-installed windows (for a different reason), this did not effect anything, after installing Windows I did a clean install of EM client, no imported settings or e-mail folders, Still having the same issues.
After numerous EM client installs, renamed account folder to force EM client to make fresh files and now I have a paid account with EM-client and a paid account with Netaddress, both accusing each other of being the problem.
I still go back to the fact that my android, IPAD and two windows mail clients all work fine, unfortunately the windows e-mail clients just do not stack up to EM client.
I have now given up… I almost always have the red triangle showing and when EM client stops receiving my e-mail I use Mailbird until EM client starts working again.