how to follow 2 email-addresses in CRM

how to follow 2 email-addresses in CRM

I have 2 mail-addresses from which I send mails to my customers.
This is because I have one email from my franchise-company and one email from my company.

For registering and for the setup I had to use my own address because there I only have the control of domain and so on.
I do not have the access nor the permission to add, change any of the TXT, CNAME SPIF etc on the franchise-site (which also would not make sense since we are more than 40 franchisees).

To have the main customer contact emails in CRM I connected the franchise-gmail-account which works good for the CRM communication. 
But now I'm facing the problem when I send out orders, invoices or other stuff outside from CRM, e.g. Books, Inventory and my customer replies to it, it only works with my company address. If I don't proof the email-address but simply answer on the mail, I do not have any mail-history in CRM.

I know I could use a bcc-address, but who thinks about that in case of sending an email every time.

Not sure if it's clear, what I'm trying to say. 

Any help or suggestion is appreciated.

Thanks
Frank