Smpt validating form
This status code should be used when the per-mailbox message length limit is less than the general system limit. This is useful only as a persistent transient error.The host on which the mailbox is resident is not accepting messages.
It used to be believed that TLS v1.0 was marginally more secure than SSL v3.0, its predecessor. Selected features specified for the message are not supported by the destination system.This can occur in gateways when features from one domain cannot be mapped onto the supported feature in another.This code should be used as a persistent transient failure.A per-mailbox administrative message length limit has been exceeded. The general semantics imply that the individual recipient may not be able to delete material to make room for additional messages.