After upgrading to firmware 5.9 the log automation option was failing when sending logs/alerts to some hosted SMTP servers with error 451.
This is because, on SonicOS 5.9 firmware the log format has been changed. The new format includes blank spaces to align different columns. The mail servers, which are returning error 451, presumably are considering blank spaces as “Bare LF”.
On DTS ID 134647, Engineering has come-up with a new option under Log | Automation called “Plain Text-Simplified” to address this issue. With “Plain Text-Simplified” selected the logs/alerts emailed will be in legacy format.
This fix will be included in SonicOS 126.96.36.199. No ETA availabe as of now when this firmware will be released. Meanwhile, a hotfix firmware can be obtained from Support.