Customer replies never delivered to the intended recipients, and never posted back to the respective RSA Community discussion thread.

The reply is actually intended for the user who responded to the customer’s question directly on the post 

However, those customer reply emails appear to have been lost somewhere as they were:-

• never delivered to the intended recipient
• never posted back to the respective RSA Community discussion thread.

Expectation:- Those customer response emails should have either been logged back to the corresponding post on the RSA Community or failed with an explicit undelivered email message.

The reply to email doesn’t work if your mail app only sends content wrapped in HTML. Hence, they are ignored by Salesforce.

Authentication protocols can be preventing your email replies from posting comments on discussion threads, i.e., Chatter.

• Switch to plain text when sending email replies to discussion posts
  
  
• The feature only allows emails that in addition to checking the replying user's email address also verifies the sender via:

1. 1. The domain owner’s Sender Policy Framework (SPF)
   2. SenderID
   3. DomainKeys

Replies are subject to the previously mentioned advanced email authentication protocols to verify the sender's legitimacy before processing the message. The server should not fail any protocols and should at least pass one security protocol in order for the email to be processed.

If the sending server doesn’t fail any of these protocols, the reply email is processed. If the server fails a protocol, the email is ignored. 

Switch to plain text when sending email replies to discussion posts

Consider these tips when sending email replies.

• Send replies from the email address specified on your profile. If you use email aliases or email forwarding services that send replies from a different email address, your replies aren’t processed.
• To bookmark, mute, like or unlike, and follow or unfollow, use the exact single word or the exact text in your replies. For example, when you want to like, enter only like (case insensitive) or +1 in the body of your email. We ignore extra white spaces or the original message that some email applications include and process the reply as a like, a bookmark, or other response. However, if you include any other text in the body, such as Like! or Like this?, we process your reply as a comment.
• We treat replies that contain your personal email signature as part of your comment. Default signatures inserted by mobile devices, such as Sent from my iPhone, are automatically removed. Before you reply, delete custom signatures and any extra text you don't want posted to Chatter. Or, add a separator line to the top of your signature to have it automatically removed. The separator line must have a minimum of one of the following characters:
  • Dash (-)
  • Equal sign (=)
  • Underscore (_)
  You can use any combination of these characters or dash dash space (-- ), which respects RFC 3676 4.3.
• We ignore attachments, @mentions, and inline images in replies.