Q:

RabbitMQ - Avoiding duplicate messages at publisher side

I am using RabbitMQ to send notifications to the user.  The user can read his queue at any time. 
The problem I am facing is that the queue is filled with lots of notifications during the night, and when the user returns in the morning, he has to process these messages sequentially.  A lot of these notifications are even duplicates. 
I guess it would make sense to improve this at the publisher side.  That is, before adding a new notification, we investigate if there are already pending notifications in the queue.  If this is the case, we only queue a new notification if it is really a new notification, hence avoiding duplicates. 
We might even go further and extend this by combining notifications: instead of simply queuing a new notification, we could replace the present notifications from the queue by a new one which holds the sum of these notifications and the new one (for example in an array of inner notifications). 
Is this possible with AMQP/RabbitMQ? 

A:

No, by default you can't replace an existing message.