7.11.2. Error handling The syslog-ng Premium Edition 7 Administrator Guide
If the connection fails, syslog-ng PE repeatedly attempts to reconnect in intervals specified in
If the connection is successful, but the message is not accepted, syslog-ng PE attempts to resend the message N times regardless of the reject being a hard or a soft reject. The number of attempts is specified with the option
If the message was sent to two addresses and only one address fails, the retry will still apply for both addresses. The assumption is that the destination will be used with a local SMTP server acting as a relay, and the local server will handle all the edge cases.