https://www.plesk.com/kb/support/unable-to-rename-or-remove-a-domain-in-plesk-mailmng-outgoing-failed-erroroutgoingno-backend-db-entries-were-modified/
Unable to rename or remove a domain in Plesk: mailmng-outgoing failed: ERROR:outgoing:No backend DB...
Symptoms Unable to manage domain settings (rename a domain, change a hosting type, add an email account, etc.): mailmng-outgoing failed: ERROR:outgoing:No...