You can click on any email address in Ezekia and this will open your email client with the 'To' address filled in. A BCC address is also populated, so that when you send the email, it will also be stored against the right person in Ezekia.
The BCC address is always the same for your firm, so you can store it as a contact in your email client, and then forward any replies you get to it. As long as the person sending the email exists in Ezekia, the email will be stored against them.