The present invention provides a method, apparatus and system for sending a message, and a storage medium. The method for sending a message comprises: a client edge (CE) node receives a specified Internet control message protocol (ICMP) message sent by a provider edge (PE) node, and determines whether the specified ICMP message carries a mark indicating that an underlying network does not support fragmentation; if yes, generate, using a maximum transmission unit (MTU) in the specified ICMP message, a path maximum transmission unit (PMTU) that does not support fragmentation; send, by means of fragmentation, an IPV6 message with a length greater than the PMTU that does not support fragmentation.