Mass Mail: How to hide @mailer1.zohocrm.com

Mass Mail: How to hide @mailer1.zohocrm.com

Hi,

Up until recently only my name apperead in the from field when i sent a mass email.
Now, without changing anything, a long string appears which contains @mailer.zohocrm.com.
How can i reevert it back to how it was before.

Thx.

Regards