7. A computer program product for assisting a user in selecting a desired hashtag, the computer program product comprising a computer readable storage medium having program code embodied therewith, the program code comprising the programming instructions for: parsing, by a hashtag selector connected to a plurality of client devices, text of a composed message to determine a topic of interest, a sentiment and a target audience of said composed message prior to being posted on a social network system; evaluating, by said hashtag selector, historical and current communications for said target audience who will be receiving said composed message to identify hashtags that are trending on said topic of said composed message and related topics to said topic of said composed message; evaluating, by said hashtag selector, historical and current communications for said target audience who will be receiving said composed message to identify hashtags that match said sentiment of said composed message prior to posting said composed message on said social network system; determining, by said hashtag selector, propagation speeds of said identified hashtags; generating, by said hashtag selector, a recommended hashtag to be populated in said composed message that will increase a propagation speed of said composed message and emphasize said sentiment of said composed message based on identifying said hashtags that are trending on said topic of said composed message and related topics to said topic of said composed message, identifying said hashtags that match said sentiment of said composed message and determining said propagating speeds of said identified hashtags; and populating, by said hashtag selector, said composed message with said recommended hashtag that will increase said propagation speed of said composed message and emphasize said sentiment of said composed message.
7. A computer program product for assisting a user in selecting a desired hashtag, the computer program product comprising a computer readable storage medium having program code embodied therewith, the program code comprising the programming instructions for: parsing, by a hashtag selector connected to a plurality of client devices, text of a composed message to determine a topic of interest, a sentiment and a target audience of said composed message prior to being posted on a social network system; evaluating, by said hashtag selector, historical and current communications for said target audience who will be receiving said composed message to identify hashtags that are trending on said topic of said composed message and related topics to said topic of said composed message; evaluating, by said hashtag selector, historical and current communications for said target audience who will be receiving said composed message to identify hashtags that match said sentiment of said composed message prior to posting said composed message on said social network system; determining, by said hashtag selector, propagation speeds of said identified hashtags; generating, by said hashtag selector, a recommended hashtag to be populated in said composed message that will increase a propagation speed of said composed message and emphasize said sentiment of said composed message based on identifying said hashtags that are trending on said topic of said composed message and related topics to said topic of said composed message, identifying said hashtags that match said sentiment of said composed message and determining said propagating speeds of said identified hashtags; and populating, by said hashtag selector, said composed message with said recommended hashtag that will increase said propagation speed of said composed message and emphasize said sentiment of said composed message. 12. The computer program product as recited in claim 7 , wherein said composed message comprises one of the following: an electronic mail message, a social media post, an instant message and a short messaging service message.