Sierra Mail Preview pane stuck closed

I just now stumbled upon the answer! You must first be sure you're NOT in the classic layout. (Mail/Preferences/uncheck the classic layout.) Then, put your cursor on the far right side of the Mail screen until you get the sideways "T" cursor (not the double arrow cursor that enlarges the screen.) With the sideways "T" cursor, drag the right-hand edge of the screen to the left. At first, it will look like nothing is happening, but keep going left and then the Preview Pane will appear like magic. Once you select a message, then the Preview Screen will populate. Good luck! 😉

Yes dragging works. I worked with the full screen mode and 5 lines open in message, then dragged about half way across the iMac. Bingo!

I have just been driven insane for over an hour trying to get the up arrow to reveal my preview pane. I'd expanded the list so I could do some bulk deletion of a way too big inbox - and the preview pane wouldn't re-open. I tried everything advised in this post and nothing worked. NOTHING! Frustration set in and in a fit of pique I furiously rubbed the arrow up and down the mail list, keeping the trackpad pressed down - and suddenly, which I wasn't expecting at all, after a few shoves, the pane reappeared! YAY! I had been trying to stay in the zone of the dot and the bottom line, but moving the arrow into the mail list section itself did the trick for me. I no longer need gin!

Before proceeding , if you open IMAP account there are three columns and if you drag ( by placing the cursor over the vertical lines joining the columns ) to extreme right and once again you try to drag towards left side it is malfunctioning and you are not able to to view the third column ( preview window ) .Is the issue similar to it ?

THANK YOU! I've been fighting with this for more than an hour.

Thanks bazzist I've been racking my brain for days as to this solution, this worked for me 👊 🙏

I have tried this multiple times I still cant get it to work.?

any suggestions.

You saved me!

Omg THANK YOU!!!! Lol This has been driving me crazy FOREVER! Just did what you said and it's fixed!!!! Thank you, thank you, THANK YOU! Lol

So happy it worked for you! Thanks for letting me know!

Thanks so much! Now I can do SOMETHING ELSE with my weekend! 😉

Thanks! Phew.

This is the only fix! Took about 10-15 attempts and PREVIEW is back. Thank you.

Well, for crying out loud. It works. Thank you.

I was baffled by this too, but finally managed to get it back. Go to preferences and select 'Use Classic Mode', then drag the preview pane up from the bottom (as you would have done on the far right edge but instead from the far bottom edge). Go back to preferences and untick 'Use Classic Mode', the preview pane should magically reappear on the right hand side.