When you see emails with "via" or "on behalf of" in the sender details, it typically indicates that the email was sent through a third-party email service rather than directly from the sender's domain. Here’s why this happens:

1. "Via" (Sent via another service)

• This appears when an email is sent using a third-party email provider (e.g., Mailchimp, SendGrid, Google Groups) instead of the sender’s own domain.
• Email providers include this to help prevent spoofing and phishing by making it clear that the email was sent through an intermediary.
• Example: If a company uses 5YMail to send marketing emails, you might see something like: "marketing@company.com via 5ymail.com

2. "On Behalf Of" (Delegate or Service Sending)

• This occurs when someone delegates email sending to another person or service.
• It is common in organizations where assistants send emails on behalf of executives or when tools like Outlook allow others to send emails on your behalf.
• Example: If John Doe’s assistant sends an email on his behalf, it might show as: "Assistant Name assistant@company.com on behalf of John Doe johndoe@5ymail.com"

3. How to Avoid "Via" or "On Behalf Of"

• Use Proper Email Authentication: Ensure SPF, DKIM, and DMARC records are correctly configured.
• Send Emails Directly from Your Domain: Avoid using third-party senders unless necessary.
• Configure SMTP Settings Correctly: If using services like Gmail with a custom domain, set up SMTP authentication properly.

4. To check and fix your email domain's configuration and prevent "via" or "on behalf of"

• Configure SPF (Sender Policy Framework)
• Configure DKIM (DomainKeys Identified Mail)
• Configure DMARC (Domain-based Message Authentication, Reporting & Conformance)