Mark as unread

`↑ Shift` + `K`

All hotkeys for Yahoo Mail

Messages and conversations Reply to a message	`R`
Messages and conversations Reply all to a message	`A`
Messages and conversations Forward a message	`F`
Inbox Mark as read	`K`
Inbox Mark as unread	`↑ Shift` + `K`
Inbox Star/Unstar a message	`L`
Messages and conversations Print message	`P`
General commands Sends the selected messages to the Trash	`Del`
Messages and conversations Add sender to contacts	`↑ Shift` + `C`
Inbox Press 1-9 to move message to one of your first 9 folders	`D`
Inbox Create a new folder	`Ctrl` + `↑ Shift` + `E`
Attachment previews Previous attachment	`←`
Attachment previews Next attachment	`→`
Messages and conversations Highlight the previous card in a conversation	`,`
Messages and conversations Highlight the next card in a conversation	`.`
Inbox Highlight the next message	`↑ ↓`
Attachment previews Switches to expanded view from side by side mode	`Ctrl` + `F`
Attachment previews Returns to previous mode	`Esc`
Attachment previews Zooms in on a document	`Ctrl` + `+`
Attachment previews Zooms out on a document	`Ctrl` + `-`
General commands Archives the selected messages	`E`
General commands Check mail (jumps to Inbox)	`M`
General commands Check all mail (includes POP accounts)	`↑ Shift` + `M`
General commands Compose a new email	`N`
General commands Toggle Preview Pane	`V`
General commands Search	`S`
General commands Turn on voice command	`Ctrl` + `↑ Shift` + `S`
General commands Turn off voice command	`Ctrl` + `↑ Shift` + `X`
Compose Attach files (one at a time)	`Ctrl` + `↑ Shift` + `U`
Compose Save as a draft	`Ctrl` + `S`
Compose Send message	`Ctrl` + `⤶ Enter`
Compose Underline	`Ctrl` + `U`
Compose Bold	`Ctrl` + `B`
Compose Italics	`Ctrl` + `I`
Compose Strikethrough	`Alt` + `↑ Shift` + `5`
Compose Align Left	`Ctrl` + `↑ Shift` + `L`
Compose Align Right	`Ctrl` + `↑ Shift` + `R`
Inbox Check/Uncheck a message	`Space`
Inbox Select all messages in view	`Ctrl` + `A`
Inbox Move focus up or down the list (preserving selection)	`Ctrl` + `↑ ↓`
Inbox Move to the previous tab	`[`
Inbox Move to the next tab	`]`