Why are my email campaign messages going to the Promotions folder instead of the inbox?

Emails sent through the campaign module are delivered using the system’s internal email server, not your connected Gmail or SMTP account. Because of this, they don’t appear in your Gmail Sent folder or Vtiger inbox, and Gmail may categorize them as Promotions. 
Additionally, if your DNS records are not fully configured, it can affect email deliverability and increase the chances of your emails landing in the Promotions folder instead of the inbox.