Lightning Experience, nothing happens. This issue occurs because Salesforce Enhanced Email — a sales productivity feature in Lightning Experience — requires that the user's profile have Read access to both the Contact object and the Lead object, including their Email fields. If the user's profile is missing these permissions, the Reply All, Reply, and Forward email action links are non-functional.
For example, a Sales Representative working in Lightning Experience attempts to reply to a customer email directly from the Activity timeline on an Opportunity record. Clicking "Reply" produces no result. This is typically caused by a profile that was not updated when Enhanced Email was enabled in the org.
To resolve the issue of Reply, Reply All, and Forward actions not working in Salesforce Lightning Experience Enhanced Email, verify that the affected user's profile has Read access granted on the Email field for both the Contact and Lead objects. Enhanced Email requires access to both objects — missing either will prevent the links from functioning.
If Read access is missing for either object, edit the profile to grant the required permissions, save the changes, and have the user test the Reply, Reply All, and Forward actions again.
Additional Resource:
Reply, Reply All and Forward emails in Lightning Experience
000383507

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.