Since two days I haven ́t been able to receive any mails by using eM-Client. I can get the mails by using Aquamail (Android-App) and using the Gmail-interface that I don ́t really like. I have always been satisfied. I have Windows 10 with regular updates and use Kaspersky Total Security – I have already tried to deactivate Kaspersky e-mail-protection, but it didn ́t work. I can send e-mails and send/receive mail from my gmx-account. I have tried to repair and reinstall eM Client – no chance. I also checked my Gmail-account. I don ́t know why, but IMAP was deactiveted – I activated it, but it also didn ́t work. I don ́t know if it is an issue of eM-Client or Gmail (Gmail has some new features and obviously it changed the settings. The Gmail-settings in eM Client are also OK, I have checked them. I also updated the database of eM-Client and I tried to restart the computer… I clicked on “diagnose” of IMAP, but no idea where this log-file is. It might help you to find the problem…
Yours sincerely
Andrea
Generally if you can send but not receive, that is an anti-virus application that is blocking the port. Try disabling Kasperky completely, not just the email protection.
If that does not work, and as it is an IMAP account, why not remove it from eM Client, then add it again?
Thank you… I don ́t know how to remove it and add it again? You mean remove the account completly? And what to do with Kaspersky – I have just bought the new licence… Shall I buy another virus protection? I don ́t dare to use Windows with Windows Defender…
I have just disabled Kaspersky (but I didn ́t remove it): nothing happened. No mails…
Interesting: It is synching only the junk-mails (screenshot) (the notification of your answer was also in the junk). I have also checked “all mails” and “all unread mails” – yesterday ́s and today ́s mails are missing.
If you go to Menu > Tools > Accounts, then click on the bin icon next to the account. That will remove it from eM Client. Then to add it again, click on the + icon, and enter your email address in the Automatic Setup.
There are many users who have Kaspersky. It is possible to use it with eM Client, but you will need to check with their documentation how to enable applications and ports.
There is nothing wrong with Windows Defender. It is actually an excellent anti-virus application, and being built-in to Windows it works better than third-party applications.
I have removed the IMAP-account and it got even worse. All my rules are gone and all my mails are gone. The subfolders are also gone. On Gmail everything is there. 
I am very, very upset.
Right, so now add it again.
I
I always get this message…
Jay Ogram, who regularly comments on this forum and who uses GMail should be on a little later. I am sure he will be able to help you further.
But in the meantime, check that you are using the correct IMAP settings for GMail. The port should be 993 and the security policy set to Use SSL/TLS on special port (legacy). Once that is set, disable Kaspersky and see what happens.
Thanks for the screenshots Andrea. That will be extremely useful to others. As I don’t use that application, I can never offer suggestions of how to change the settings. 
Thanks a lot! I have another problem now: I cannot apply all of the rules, some mails don ́t appear any more… (I have folders for my favourite persons!)
When removing and adding accounts, the Rules can become broken, especially those involving folder names or account names. Open Rules and check that the ones that don’t work are pointing to the correct folder.
That ́s what I did… but mails between 2011 and 2018 are missing. I still have them on the Gmail-Server, but I often use eM to find old mails. I corrected all the missing folders in the rules. Most of the missing mails are in the folder “all mails”, but trying to apply the rule on this folder doesn ́t work. I have to move or copy all the mails manually… I loved the view of mails from the same address on the right side. Now I consider even a change of the mail client. I have been a satisfied user of eM for a long time…
Now the mails also in my mobile client disappeared… (AquaMail). I only have archive mails from 2007 till 2011, and the brandnew ones. On the Gmail Server there is everything there… but I don ́t dare to synch anymore, I am afraid the mails will also disappear on Gmail…
I think if the same issue is there on your phone, then it is some problem with GMail. Maybe some GMail users can assist you further.