When you are composing a message in Send Photos window you can also use the Preview button to check how the sent message will look like. Preview is the truthful representation of the sent message.
To generate it the program uses the base photo size you chose for that recipient, rotates photos automatically if an orientation tag is found in their EXIF information and assembles everything using the selected template.
Therefore what you see in the Preview is what your recipients will get in their e-mail clients.

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