Have you ever had anyone tell you this: “Hey! The picture you sent me doesn’t show up in my mail!” They could be using Thunderbird. John Carter offers this solution: "Direct them to this link and it will tell them how to configure Thunderbird to display images.
"However, it could be that what you did was take a screenshot (saved to the clipboard instead of to the Finder) and pasted it into your e-mail from the clipboard.
'I have been in the habit of taking screenshots on my Mac using Shift-Command-Ctrl-4. This saves that selection to the clipboard. Then I paste the contents of the clipboard into an e-mail message.
John explains, "When taking a screenshot, what gets saved to the clipboard is a PNG formatted image (the default format), and that shouldn’t be a problem, but what gets pasted into the email message is a TIFF formatted image. Isn’t that nice! Thunderbird will not display a TIFF image! So when I do that, anyone using Thunderbird (my wife, when she is using her Linux PC) won’t see the image. There may be other mail apps that won’t display TIFF images. Mac Mail will.
"Mozilla’s explanation for not displaying TIFF images in Thunderbird is that TIFF is the only image format that gets transmitted as one large packet. All other image formats get broken up into smaller packets. Mozilla chooses not to waste time collecting such large packets.
"There is a preference that can be set that tells OS X (any version) to collect screenshots as JPG instead of the default PNG (see this), but even though that is done, when you paste a screenshot image from the clipboard into Mac Mail it always converts the image format to TIFF. And this only applies to clipboard images taken with screenshots. Other clipboard images, like when you copy a file to the clipboard, are not so affected.
Ready for John's how-to! "So here’s the easiest way to include a screenshot in an e-mail:
1. Take the screenshot using Command-Shift-4. This saves the image to the Desktop in JPG format (the default).
2. Use one of the following three ways to get the image into the message:
a. Copy (Cmd-C) the file, then paste (Cmd-V) the image into the message body
b. Drag the file into the message body
c. Click on the paperclip icon in the Toolbar and select the file.
"And remember, don’t include a TIFF image in an e-mail message. Any other image format is okay."
And here's John's final touch: "From a Mac point of view, the best solution would be to not reformat a clipboard screenshot into a TIFF when pasting into an e-mail message."