Q & A > Error Codes > SMTP

• 250 OK Response
• 552 Requested mail action aborted: exceeded storage allocation
• 550 Mailbox not found
• 454 4.7.0 Temporary authentication failure
• 530 5.7.0 Authentication required
• 535 Authentication credentials invalid
• 452 Too many recipients
• 452 Requested action not taken: insufficient system storage
• 451 Requested action aborted: local error in processing
• 450 Requested mail action not taken: mailbox unavailable
• 421 Service not available, closing transmission channel
• 251 User not local; will forward
• 554 5.3.4 Message too big for system