If you are seeing Invalid Content or Content contains characters that cannot be sent in a text message, when composing a message, it means that your message contains characters that are no accepted by the wireless carriers, so we can't allow you to send the message. Below are the characters supported by the wireless carriers for short code messaging.
The following characters are the most popularly used though: a-z, A-Z, 0-9 and these special characters: .,:;!?()~=+-_\/@$#&%
While Tatango does accept the characters in the table above, we can't guarantee they will show up on an individual's phone. This is a carrier issue. For example, an ñ may show that it went out on system with no problem, but on an iPhone it will show up as a question mark whereas every other phone is fine. Sticking to the standard English characters is the best way to go.