With more and more email services blocking accounts for mass mailings, it would be easy to add an Email Delivery Throttle setup value to set the number of Emails Sent per minute the Email Engine can send.
Once the number of emals per minute is reached, the engine waits till the next minute to resume the remaining emails with same process.
Is there any update on this one?
This is a common issue with smtp.office365.com
https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#sending-limits-1
Limiting the amount of emails sent per minute is only half the problem solved, as other tools and even users may be sending mail by the same account that Knowledgesync would be unaware of causing the sending limit to be encountered.
SMTP Error Codes:
4xx = Temporary failure → retry later.
5xx = Permanent failure → don't keep retrying.
Currently KnowledgeSycn just treats emails as either sent, not sent, failed to send (number of times).
It'd be good if 4xx errors were treated as a retry, but don't count the failure.
Both fixes combined, a known limit per minute added and the ability to handle retries without counting it as a real failure should solve this problem.