Can I Customize the Proposal Emails that are Sent to Buyers on Connect?

Unfortunately this is not available as a feature. The message that Buyers receive is a pre-set template that is sent automatically from Brandboom and cannot be modified.

To get an idea of what the Buyers see, see the article What will the Buyer see when I send a proposal?

If you are want this added to Brandboom as a feature, please contact Support.