I tried to send someone an email with a PNG format image attachment but it was stopped by their email filtering software (messagelabs).
They said I could send them the image in a JPG or ZIP format file.
I'm assuming they are blocking this format for security reasons. But, what about the PNG format is potentially unsafe?
Are there any known security vulnerabilites in it? (I've only found something very old.)
Is it possible to include executable or other malicious code in the format?