Email Delivery: Email Service Providers Imposing IP Block on Salesforce Outbound Email IP's
|Knowledge Article Number||000233454|
Outbound emails from Salesforce may bounce when sending to some Email Service Providers (ESP). The bounce message may vary, however the failure reason will typically indicate that a specific IP address has been blocked.
Large ESP's such as Microsoft, Yahoo, Google Mail, AOL, can potentially impose an inbound IP Block/Throttle for specific Salesforce IP’s. This will cause emails from some Salesforce Organizations to temporarily or permanently bounce.
The behavior could stem from the introduction of a new IP, as the reputation has not matured; however it could also occur from a large influx of emails from a Organization to number of recipients on the same domain. The latter could trigger red flags on the recipient server as it may appear to be suspicious or malicious. Generally, when the issue does occur, the block is limited to a small subset or IP's.