When I sent an email from Email Marketing in v16, it was received in the promotion tab in the receiver's mailbox.

Is there anything I can do to ensure that participant user must receive the mail in their Inbox as important/primary mail?

For your information

 
List of, what I have already performed?

• First direct mail to a recipient.
• Send a mail through the campaign.
• Try different subject lines.
• Changing the subject lines and contents.
• I also tested sending to different recipient accounts.

In all the scenarios The mail was received in the promotion tab.

• I have not sent any bulk emails from this mail for marketing.
• Also, I do not want to send bulk emails as marketing, Just want to be informative to every customer. 
• What points should be considered in account when I set up a mail or campaign in Odoo v16?
• Any suggestions will be appreciated.