A user is not able to change the "From" email address when sending an email in Salesforce UI from standard/custom objects and even the global publisher actions. The field "From" is empty and greyed out as following :
This behaviour is specific to two particular users with different profiles. Other users with same or different profiles and perm sets are able to chose between the defined org-wide address or their own email address. I have spent the whole day comparing between profiles/perm sets, searching online, checked email deliverability to "All email", access to Task/Activity, "Send email" permissions ... but with no luck. I have also repeated the steps in the following article with no success as well.
What might be the issue ?