Outgoing mail control rejects outgoing mail before the limit specified on a mailbox, domain or a subscription level has been reached.
For example, limit of outgoing mail for a mailbox is equal to 250. However, messages are rejected after reaching the limit of 10 per hour with a similar error:
5.7.0 Your message could not be sent. The limit on the number of allowed outgoing messages was exceeded. Try again later..
Data mismatch between Plesk
psa database and SQlite database
/var/lib/plesk/mail/outgoing/data.db used by mail server to limit outgoing email.
Connect to the server via SSH;
Run the following command to repair
# plesk repair mail example.com
If the issue is server-wide, re-create the file for all domains on a server:
# plesk repair mail