I can't send iPhotos in email any longer.

Question

The error message is : Your email did not go through because the server did not reply. It used to work before.

Answer 1

Have you recently enabled two-step verification?
Then you may need to set up an app-specific password for iPhoto.
Other forum members reported, that creating  an app-specific password is required, see the post below:
Re: I am using iPhoto version 9.6 and I can no longer get an email sent with a photo attached. I get an error message saying the email did not go through because the server did not reply. I can send the photo with Mail. Help!in response to Gary Kissler
This solution is for those of you using 2-step verification for your Apple ID and are using iCloud as the mail server that you are trying to mail photos with.
I too had this issue. The problem in my case occurred because I had setup 2-step authentication for my Apple ID. If you have done this then you will get the error message "the mail server did not recognize your email/password...". To solve the problem go to:
https://appleid.apple.com
Click "Manage Your Apple ID"
Verify your identity with the device you selected (if this step does not show up then you have not likely set up 2-step authentication and this is not your solution)
Click Password and Security in the left column
Click Generate an app-specific password
Enter iPhoto as the name of the app
Copy the password and paste this into the password box in iPhoto where you would normally enter your apple ID (in the mail account section in iPhoto preferences).
And...voila' (I hope)