Why are some emails not being delivered?

If some emails are not being delivered from your campaigns and automations, the cause is usually one of these areas:

1. Missing or Failed Authentication: Emails without proper SPF, DKIM, or DMARC authentication may fail verification checks, causing recipient servers to reject or distrust them (Tools like MXToolbox, DMARCly, or similar DNS checkers can validate these records)

2. Spam and Content Filters: Email providers may block or redirect messages to spam due to suspicious content, excessive links, attachments, or formatting issues.

3. Poor Sender Reputation: A low-quality sender reputation caused by high bounce rates, spam complaints, or poor engagement can reduce email deliverability.

4. Full Mailboxes: The recipient’s inbox may be unable to receive new messages because their storage limit has been reached.

5. Invalid Email Addresses: Incorrect, outdated, or inactive email addresses can cause delivery failures and hard bounces.

8. Automation or Campaign Configuration Issues: Incorrect workflow rules, scheduling settings, audience filters, or sending limits can prevent emails from being sent.

9. Suppression or Unsubscribed Contacts: Contacts who opted out, bounced previously, or were added to suppression lists will not receive future emails.

10. Poor List Quality: Old or inaccurate contact lists increase bounce rates and negatively affect overall deliverability.

Updated on: 31/08/2026