Comprehensive and Detailed Explanation:
The correct answer is A - From the Reply Mail Management settings page, choose the "Create Custom Response" option under "Automated Response Email for Remaining Replies" section and select the HTML email.
* RMM allows you to define an automated response for incoming replies.
* You can specify a simple custom response and link it to a pre-built HTML email template through the RMM settings without requiring a triggered send setup.
# Why others are wrong:
* B and C: Using a Triggered Send is more complex and usually unnecessary for a simple automatic response.
* D: There's no option to paste full HTML code into Admin > Account Settings for auto-replies - that's not how RMM is configured.
Exact Extract from Salesforce Official Documentation:
Salesforce Help - Reply Mail Management Setup:
"Configure a custom automated response by selecting 'Create Custom Response' under 'Automated Response Email for Remaining Replies' in Reply Mail Management. You can link a pre-built HTML email." (Source: https://help.salesforce.com/s/articleView?id=sf.mc_es_reply_mail_management.htm)
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