I never post from my phone " iphone 6 " I tried today and wouldn't let me post a picture this message pops up Can I resize the picture on my phone or do I have to buy an app? 

No problem for me to do this on my Mac just on my iphone 

 

Dave,
I use the SimpleResize app on my iPhone before posting.
Any size below 1000x800 works fine, even above too.

good info to know about the Simple Resize app. I have had to do manual resizes for most pictures taken with a both digital camera and iPhone before posting to the forum even from my laptop; hadn't yet tried to post directly from iPhone

Dave email the picture to yourselve it will ask you to resize , once you get the email, save picture and delete original