The phrase "a challenging message" is correct and usable in written English.
It can be used when referring to a message that is difficult to understand, interpret, or respond to, often due to its complexity or the weight of its content.
Example: "The speaker delivered a challenging message that left the audience deep in thought about the implications of their actions."
Alternatives: "a difficult message" or "a tough message".
At the convention, according to a promotional brochure, Justice Thomas will share "a challenging message from his heart exclusively for C.W.A".
But it can be a challenging message to get across, sometimes, when there's no funding.
Purists will argue that offsets aren't really "donations"; they're "payments for ecosystem services" (a subtle but important distinction that underlines the value of nature, rather than the goodness of the giver), but it's still reassuring to see an entertainer reaching out to a mainstream audience with a challenging message that goes beyond the usual bromides and broadsides we're accustomed to.
The real tragedy is that even when crosses are on show, the most hopeful and challenging message they can carry often remain covered up.
"I personally believe that now is the moment for the Yemeni government to really step up and do what it has said it will do," Mrs. Clinton said after the conference, during which she delivered the same challenging message to Yemen's prime minister, Ali Mohammed Mujawar.
Messaging is a challenging problem in general.
Thus, it is a challenging problem how to transmit messages reliably and efficiently in CRAHNs.
Given intermittent connectivity and spectrum availability, it is a challenging issue regarding how to transmit messages between SUs in a reliable and effective way in CRAHNs.
But our message has been understood in Europe as a challenging defiance.
This is a challenging moment, but we must maintain the integrity of our message and moral movement.
Thus, routing messages preserving energy and network bandwidth is a challenging requirement of paramount importance.
