Salesforce.com sends email from 34 different IP addresses. If your organization blocks any of these IP addresses, users might not receive all email sent from Salesforce.com.
The Salesforce.com IP ranges are:
- 126.96.36.199 to 188.8.131.52
- 184.108.40.206 to 220.127.116.11
- 18.104.22.168 to 22.214.171.124
Whitelist above Salesforce.com IP ranges on organization’s email server. Whitelisting an IP address allows the email server to receive email from an IP address that might otherwise be blocked