What to do (workaround): Either disable Avast Mail Shield in Avast GUI or disable the conflicting apps. Please note that not all system extensions listed there must be conflicting! * * UBF8T346G9 (101.13.75/101.13.75) Microsoft Defender ATP Endpoint Security Extension The relevant are the extensions with * under 'active' in _work_extension section in this case, aside from Avast there is Microsoft Defender and CiscoAn圜onnect. * * DE8Y96K9QP .acsockext (3/3) Cisco An圜onnect Socket Filter Extension _work_extensionĮnabled active teamID bundleID (version) name How to find out potential conflicting apps: run Terminal and in it run the following command: Web Shield (web browsers) and alternative Mail clients (like Mozilla Thunderbird) are working fine in a similar situation. This is probably not caused by Avast Antivirus or any of the conflicting apps it seems like a bug in the Apple's networking library used by the mail client. What is happening: Apple Mail or similar mail app connects to mail server but fails to initialise secure connection and fails communicating. We have reproduced it with:Ĭisco An圜onnect (even installing only VPN module without actually using it causes System Extension to be started)

Thunderbird works fineĬonflicting apps: It seems any app that uses System Extension which filters network connections. Does not happen with all email clients, eg. Problem: Mail stops working with Avast Antivirus Mail Shield activeĪffected mail applications: Apple Mail, Spark (both seem to use the same communication framework), possibly more. TL DR: Temporarily disable Avast Mail Shield on Big Sur if this is happening to you.

Little snitch endpoint security