"reply to" email and "from" email

"reply to" email and "from" email

I recently upgraded my account to include the zoho mail add on. I have a corp email address that I can not bring in to zoho for security reasons. Prior to enabling the mail add on. I had the ability to add as a send from email address which worked great. Now that I have enable the zoho mail add on I can only use my @zoho.com email address. Please advise asap as to how to correct this.

Thank you.