How do I delete multiple messages all at once on my Imac

Are you talking about email messages in the Apple Mail app ? If yes, simply select as many as you want to delete by clicking on one, then, while holding down the shift key, select another further down the listing of email messages and click on it. All messages between the two will be selected as indicated by the highlighting. Then hit the delete key. That's all there is to it. If you want to delete some random email messages separated by some you want to keep, select them while holding down the command key, then hit delete. I fyou are referring to something else please elaborate.

The easiest way I know is to do it on your iPhone. Basically, on the iPhone, you open Messages, select edit in the upper left corner, click on "Select Messages" (this moves the entire messages conversations list slightly to the right and inserts a radio button for each conversation), you select all the ones you want to delete by clicking on the radio button for each, then hit "Delete" on the bottom right of the screen.

All the messages show up on my iPhone as well as my Mac, but over the years I've been deleting them from my iPhone per pokey b's advice, but that doesn't remove them from the Mac, so that's why there are hundreds there. I need to remove them from the Mac after they are long gone from the phone. Any advice?

My question concerns messages, in the messages app. I seem to have collected hundreds of conversations and need to know how to delete multiple conversations (or all of them) at once.