Please try the suggestions below, found in this post on the EasyList forum.
Add these custom filters in AdBlock
Warning: Custom filters can break websites. Use them with caution and at your own risk. Learn more about custom filters in AdBlock.
If the ads aren't removed after you reload your mail page, try clearing your browser cache and cookies.
Try the It's Not Important! userscript
If the above custom filters don't remove the ads, it may be because the ads are styled in a way that overrides the ability of the custom filters to hide them. You can try the It's Not Important! userscript, which neutralizes the overriding style. You will need to install the Tampermonkey userscript manager.
- We aren't providing step-by-step instructions for adding custom filters and userscripts. We consider these advanced ad-blocking techniques, since custom filters can break web pages and userscripts can pose additional security risks. (The It's Not Important! userscript has been thoroughly vetted by and is well regarded among the ad-blocking community.) We offer these suggestions as a courtesy for those willing to accept the possible consequences.
- We don't provide technical support for custom filters and userscripts. If a custom filter breaks a web page, remove it from AdBlock the same way you added it. If you need help with a userscript, please post your question where you downloaded it.