Scenario
A customer has reported an error on the Undelivered Email List, showing "Not sent: Blocked by mail filter."
Solution
The error "Not sent: Blocked by mail filter" indicates that the sending rate is too high, often caused by similar email messages being sent too rapidly.
To address this:
1. Navigate to List > Mailing > Undelivered Emails and verify if the From, Recipients, and Subject fields contain identical information.
2. Check the time interval between the duplicate emails. If a large number of duplicate or similar emails are sent within a short timeframe, they may trigger spam filters and be blocked.
3. To prevent such errors in the future, ensure each email message generated from your NetSuite account includes a unique identifier in the subject line. This helps differentiate between individual emails and reduces the likelihood of triggering spam filters.