Outlook Rules Can Produce Your Desired Outcome
You don't have control of A, B, or C's email program, so you cannot prevent them from sending you an email when they click Reply All.
However, you do have control of what happens when you receive the message. You can use Outlook Rules to delete those unwanted messages, producing the same result as if the email wasn't sent in the first place. I'll warn you in advance: this is a little complicated because we have to bend the rules (pun intended) to pull this off
If recipient A, B, or C presses reply-all then the reply-all should go to everyone besides me
To uniquely identify these unwanted messages, we'll examine the subject line for the presence of
Re: (to match only replies), and the To addresses for the presence our interesting recipients, then matching emails.
Caution: If you indeed have Outlook delete these messages, it will do so without notifying you. You may wish instead to have the messages moved to another folder so that you can review them before deleting them yourself.
When one clicks Reply All to a message sent to multiple recipients, the reply is addressed to everyone except the one creating the reply. Therefore we have three distinct "sets" of possible message recipients we're interested in (since you received the e-mail was assume all of these are also sent to you):
- A and B
- A and C
- B and C
Unfortunately, most of Outlook's rules, including those for examining message recipients, use "OR" logic for multiple criterion. Using ideas suggested by the MSOutlook.info article Using AND operators in rules we can work around this by using multiple rules to temporarily assign messages to categories to mimic the desired "AND" comparison in our rules.
First, we need the following three rules:
Sent to 'A', and Subject contains 'Re:' Assign to category 'Rule - A'
Sent to 'B', and Subject contains 'Re:' Assign to category 'Rule - B'
Sent to 'C', and Subject contains 'Re:' Assign to category 'Rule - C'
Now our interesting messages will be assigned two of the categories specified above. Interestingly, Outlook allows
AND operators when matching categories, so the following rules will discard our unwanted messages:
Assigned to category 'Rule - A' and 'Rule - B' Delete
Assigned to category 'Rule - A' and 'Rule - C' Delete
Assigned to category 'Rule - B' and 'Rule - C' Delete
For testing purposes, consider starting off with a rule action less severe than Delete. Perhaps use Mark as read or Move to a folder until you're sure everything's working as intended.
To keep the Outlook house clean, we should wrap things up with a final rule to
Clear categories for all messages. For example, a reply sent to only you and A will be assigned to only the Rule - A category, but we don't want to retain this category assignment after rule processing is complete.
Bear in mind that if a reply is sent to You, A, B, C, and D, these rules will still nuke the message. That's an unfortunate weakness of this approach. If it's possible this will happen, you can modify your first three rules to add an additional condition to only match messages where the text
super-secret-sauce appears in the body of the message. You would then need ensure the original message includes that key text (feel free to use something less likely to attract raised eyebrows). You see this same technique used in emails exchanged as part of opening an inquiry with a company; usually a phrase along the lines of "Do not remove this line: [ticket-id: random stuff here]"