Refreshing the Outgoing mail Control statistics at Tools & Settings > Outgoing Mail Control > Refresh fails with the following error in Plesk UI:
PLESK_ERROR: Error: External exception. String could not be parsed as XML
- Solution from the article Cannot update Outgoing Mail control: Domain does not exist does not help.
This issue is caused by Plesk bug with id #PPPM-8665, which is planned to be fixed in future product updates.