'Reply'&'Reply to All' button missing from email message feed when using custom emailpublisher

Hi i have a very simple email publisher to replace the original one :->

<apex:page standardController="Case"><apex:emailPublisher entityId="{!case.id}"        fromVisibility="selectable"        subjectVisibility="readOnly"        toVisibility="readOnly"        fromAddresses="support@abc.com}"        emailBody=""/></apex:page>

So i remove the standard 'Answer Customer' action and add in my custom emailpublisher in. Now all my email message record feed doesn't have the 'Reply'& 'Reply to All' button. What have i missed out? Basically what I want to achieve is I want the sender to default as our support email instead of user's personal email.

With Answer Customer Action

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Without Answer Customer action (replaced with my custom email publisher)

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