SMTP logs

Here are the meaning of SMTP status codes.

Status Code	Description
211	System status, or system help reply
214	Help message
220	Service ready
221	Service closing transmission channel
250	Requested mail action okay, completed
251	User not local; will forward to
354	Start mail input; end with “.”
421	Service not available, closing transmission channel
450	Requested mail action not taken: mailbox unavailable
451	Requested action aborted: local error in processing
452	Requested action not taken: insufficient system storage
500	Syntax error, command unrecognized
501	Syntax error in parameters or arguments
502	Command not implemented
503	Bad sequence of commands
504	Command parameter not implemented
550	Requested action not taken: mailbox unavailable
551	User not local; please try <….>
552	Requested mail action aborted: exceeded storage allocation
553	Requested action not taken: mailbox name not allowed
554	Transaction failed