Hi,
How to add custom columns to Emails? I would like to add columns with Accounts and Contacts. I’d like to see the name of the company or person who sent the email.
Thanks
You can customize the listview layout from Studio and add/remove columns that are standard to that module. To do so you need to go to:
Studio > Emails > Layouts > List View
There is a field called Parent Type that can provide you information about the Module the email is related to if a relationship exists.
Check this link for custom columns:
I know how to make other relationship but I don’t know how to make this relationship 
Could you give me some tips on how to make this relationship?
Don’t think it is an easy task you have. When you receive an email, it’s not part of the db until you import it. What you see under emails is a list of emails as you see them on a email client. To accomplish what you need you might need to modify the Emails module code on the back end.
Here is the documentation on the standard behavior on emails from SuiteCRM:
https://docs.suitecrm.com/admin/administration-panel/email/
Developers Guide:
https://docs.suitecrm.com/developer/
Hope you can find a solution!