Hey @mark_saunders,
Appreciate your waiting while I consulted with our engineers on your questions-- I wanted to make sure I was 100 percent certain of my answer before replying.
At the moment, using a rule to log an email to Salesforce cannot log to an Opportunity. It can only log to a Lead or Contact.
It’s important to note that using a rule to log an email does not rely on BCC, rather, we use the Salesforce API to import the message in Salesforce.
Our system will try to find a Lead or Contact in Salesforce that matches the contact of the conversation (via email, phone number, etc...) and attach the message to it.
Each use case is different, so it’s tricky to implement a default behavior that will satisfy all of our customers. Instead, we’ve set up the log action do the minimum (import message in Salesforce attached to the relevant Lead or Contact) in order to not make assumptions about the workflow the customer wants to apply in Salesforce.
However, it seems like there may be demand from your team for a more granular approach to this logging action. I highly recommend submitting a feature request in our Ideas Portal.
I think that covers your questions, but if I’m misunderstanding, or if you have any follow-up questions, please ask away :-)