The gemarah in Megillah (15a) states:
“And they told Esther’s words to Mordecai” (Esther 4:12), but he, Hathach himself, did not go to tell him directly. The Gemara explains: From here we see that one does not bring back a sad report.
This statement is made to explain why Hatach did not bring Esther's response about not being able to enter to see the king without being called. However, just before that Hatach did bring a 'sad' report to Esther from Mordechai wherein he explained to her about Haman's plan to kill the Jews.
Hathach went out to Mordecai in the city square in front of the palace gate; and Mordecai told him all that had happened to him, and all about the money that Haman had offered to pay into the royal treasury for the destruction of the Jews. He also gave him the written text of the law that had been proclaimed in Shushan for their destruction. [He bade him] show it to Esther and inform her, and charge her to go to the king and to appeal to him and to plead with him for her people. When Hathach came and delivered Mordecai’s message to Esther, (Esther 4:6-9)
At first blush this would seem to me to fall under the category of "one does not bring back a sad report" yet it must not be so if Hatach delivered it. Therefore I would like to better understand what the parameters of 'one does not bring back a sad report.' in fact are. Is it up to the messenger to decide if something is sad/ruinous enough? Are there any other ways to tell if a certain report should or should not be delivered?