A Sending Quota Exceeded Error occurs when a mailbox exceeds its daily limit for sending emails. This error is typically triggered to prevent potential damage or suspension of the mailboxes.
The daily email limit increase on fresh mailboxes per daily sending limits. Taking this in consideration will make this error extinct :
Day 1: 1 email
Day 2: 10 email
Day 3: 25 email
Day 4: 50 email
Day 5: 100 email
Day 6: 500 email