I received a campaign at my gmail account, why does the from domain include "via---..."?

I received a campaign at my gmail account, why does the from domain include "via---..."?

Gmail will display this additional information when Email Authentication is not setup for the sending domain.  

For instructions on how to authenticate you domain, please refer to this article: Authenticate your email domain.

If you have any further questions regarding authentication, please email our Support team at support@delivra.com