Seeking simple and inexpensive CRM tool for following up with clients

I work for an environmental non profit that supports other organizations with funding. When onboarding new grantees ("clients") we require a few pieces of documentation to be signed – following up on these docs with partners is time consuming. it'd be great to have an email-integrated tool that supports automating the follow ups instead of relying on memory or spreadsheet tracking. Looking for a tool that integrates well with outlook and that doesn't over complicate things.