As a new user we're setting up all our clients/leads/contacts. But old emails don't get pulled in to the records.

As you pull all emails in to the inbox feature, could you also pull old emails related to an email address against an old client/lead/contact and store them against that record?

As a continuous user this also works for new leads. If a lead comes in to my inbox, I'll then set them up as a lead in CRM. But that first email won't be stored as the record didn't exist when the original email came in.

An alternative (possibly easier) workaround would be to provide a feature where you can select an email and choose to add it to a client/lead/contact record.