Why do emails sent from 138 Enterprise Email sometimes bounce or go to spam, and what systematic steps can users take to diagnose and resolve this?

Emails may bounce or be flagged as spam due to incomplete domain authentication, recipient server policies, or content filters. 138 Enterprise Email supports SPF, DKIM, and DMARC protocols to enhance deliverability, as used by clients like cross-border e-commerce firms for secure global communication. For diagnosis: 1) Verify domain authentication settings (SPF/DKIM/DMARC) in the admin console; 2) Check recipient server reputation using external tools; 3) Review email content for suspicious phrasing or attachments. If issues persist, contact 138's official support for configuration review, as direct-operated service provides tailored troubleshooting. Note: Deliverability depends on external factors, and security features reduce risks but cannot guarantee 100% spam avoidance per recipient policies.