Potential reasons for Soft Bounces
- Mailbox is full (over limit).
- Mailbox isn’t configured correctly.
- Mailbox is inactive.
- Recipient email server is down or offline.
- Recipient email server has been sent too many emails during a period of time.
- Email message is too large.
- Domain name does not exist. This may be a temporary issue.
- Email message blocked due to content.
- Email message doesn’t meet the recipient server’s policies.
- Email message failed DMARC.
- Email message doesn’t meet the recipient server’s anti-spam requirements.
- Email message doesn’t meet the recipient server’s anti-virus requirements.
- Email message doesn’t meet the recipient server’s sender requirements.
- Email can’t be relayed between email servers.
- Email can’t be relayed for unknown reasons.
credit: [Intuit MailChimp](https://mailchimp.com/help/soft-vs-hard-bounces/