At this time archiving policies are still managed through archive tags in the legacy Exchange Admin Center (soon they'll move to the Compliance Center too). An archive tag will work independently from any retention policies you setup on the mailbox so what you can do is create one archive tag for 2 years after item is sent/received and then create a retention policy (in Information Governance solution of the Microsoft 365 Compliance Center) to retain and then delete after 5 years.