How to send calendar invitations / responds with my main email which is not the same as my calendar account

Good day!

We have the following problem on eM Client after switching from MacMail:

  1. IMAP mail account (Default mail) [email protected]
  2. iCloud account for mail and calender: [email protected]

Whenever I receive an invite on my [email protected] and I respond by selecting the YES/NO/MAYBE the email with the answer is now sent back using the email address.

How can we fix this?
Thank you!