I have experienced the following problem:
I installed Avast Antivirus (Free version) on my MacBook. Soon after, I noticed long delays with Google mail syncing with my email clients (I use apple mail and Spark) on all of my devices (MacBook, iPhone, iPad). In fact my apple mail app said that it couldn’t connect to gmail imap. Using a web browser or the google mail app, there was no problem.
I uninstalled Avast Antivirus from my Mac and a while later google mail returned on all devices.
I then reinstalled Avast Antivirus and the problem returned!
I have uninstalled the program again and, after a delay, gmail is again working fine.
It does appear that Avast Antivirus is in some way interfering with google mail imap. I see that there have been reports of similar issues in the past. I am reluctant to install Avast again. Is there a solution to this issue?