Salesforce provides a number of settings to manage the deliverability of emails sent from your org. You can turn deliverability off, so your org only sends out password reset emails, or restrict email sending to system emails. Go to Setup > Administration > Email > Deliverability to manage the settings. The Salesforce help provides guidance on how to use these settings.
Deliverability settings can be used to reduce the likelihood of email sent from your Salesforce org being categorized by your email system. To improve deliverability, your IT administator may need to add your Salesforce domain or Salesforce IP addresses to a whitelist or an allowlist in the email system.