Lohit,
I would suggest you to re-think the design approach that you are currently following as it is not a good practice to publish a huge message to UM, you can try other integration patterns.
If you are sure to go with the current approach, make sure you also check other factors like network, CPU, memory, disk space (persist the message) etc.,
There is no hard limit on MaxBufferSize but the above factors will play a role. Make sure you do a benchmark testing in your lower environments like (pre-prod/QA) with the expected volumes of messages.
#Universal-Messaging-Broker#Integration-Server-and-ESB#webMethods