Monitoring email misuse is crucial for ensuring security and maintaining your email service reputation. Here are some common signs of email misuse you should watch for:

1. High Volume of Outgoing Emails: If you notice a sudden increase in the number of outgoing emails, it could indicate that accounts are compromised or being used to send spam.
2. Unusual Login Patterns: Track login attempts from unusual IP addresses or countries, especially if they occur at odd hours or outside typical user locations.
3. Email Bounces or Delivery Failures: Excessive email bounces may indicate an attempt to spam invalid email addresses, damaging your IP reputation.
4. Spam Complaints: Monitor feedback loops from major email providers (like Gmail, Outlook) for spam complaints linked to your domain, as these can escalate to blacklisting.
5. Abuse of Forwarding: Ensure forwarding rules are not being set to forward all emails to external addresses without user knowledge, which could be a sign of account compromise.
6. Phishing and Malware Links: Check emails for suspicious links or attachments that could deliver malware or attempt to steal credentials.
7. Suspicious Content: Regularly audit outgoing emails for flagged terms often used in phishing or spam emails, like “urgent,” “act now,” or promises of quick gains.
8. Unauthorized Use of Aliases: Verify that users are not creating aliases to impersonate others or send unauthorized messages.
9. DKIM, SPF, and DMARC Failures: Ensure these protocols are configured properly and monitor for failures, as misuse may indicate spoofing attempts or compromised accounts.
10. Excessive Use of Certain SMTP Commands: Abnormal use of certain commands (like RCPT TO or MAIL FROM) could suggest attempts to probe or misuse your SMTP server.

By setting alerts and establishing limits for each of these areas, you can catch potential misuse early and protect your server and IP reputation.

Email Bounces or Delivery Failures differintiate this?

“Email bounces” and “delivery failures” both indicate issues with sending emails, but they have distinct meanings and causes:

1. Email Bounces

• Definition: A “bounce” occurs when an email is returned to the sender because it couldn’t be delivered to the recipient’s email server.
• Types:
  • Soft Bounce: Temporary issues that prevent delivery, like a full mailbox or a server being temporarily unavailable. The email might be retried by the sending server.
  • Hard Bounce: Permanent issues that prevent delivery, such as an invalid email address or a domain that doesn’t exist. Hard bounces are a sign of bad recipient data or an outdated email list.
• Indicators:
  • Bounce reports often include details like “Mailbox full,” “User unknown,” or “Domain not found.”
  • Tracking high bounce rates can indicate problems with recipient data quality or list management.

2. Delivery Failures

• Definition: A broader term referring to any instance where an email fails to reach the recipient’s inbox, covering a range of issues beyond bounces.
• Causes:
  • Blocked Emails: Email is rejected due to spam filters, blacklists, or recipient server policies.
  • Spam Folder: Delivery failures may also refer to emails that land in the spam folder rather than the inbox, usually due to content or sender reputation issues.
  • Server Issues: Network or server issues on either the sender’s or recipient’s end can prevent delivery.
• Indicators:
  • Delivery failures may not return as “bounced” messages. Monitoring tools like delivery reports, bounce logs, or feedback loops help to track these.
  • High delivery failure rates might point to content, IP reputation, or email server configuration issues.

In short, bounces specifically refer to rejected emails that are returned to the sender, while delivery failures encompass any scenario where an email doesn’t reach the inbox (whether it bounces, is blocked, or is marked as spam).