10. The non-transitory computer-readable medium of claim 9 , wherein only a subset of the created lexical variants of the message text is sent to the one or more communications devices and a D-optimal design is used to determine the subset.
9. A non-transitory computer-readable medium comprising computer program code that, when executed by a communications system including a communications server in communication with one or more communications devices, enables the communications system to perform the following method for optimizing a message text: receiving on a communications server a message text comprising a plurality of words or word phrases that combine together as non-overlapping parts of the message text; treating the non-overlapping words or word phrases of the message text as multiple independent variables that are reduced to a message vector having each of the multiple independent variables as components of the message vector; automatically creating on the communications server a plurality of lexical variants of the message text, wherein the lexical variants are created by replacing a word or word phrase for each of the multiple independent variables with one or more alternate words or word phrases based on one or more value-changing rules being applied to the received word or word phrase in the message text, the lexical variants for each of the multiple independent variables being reduced to a lexical vector such that the message vector is made up of variable-sized lexical vectors; sending each of the plurality of created lexical variants of the message text to the one or more communications devices; measuring a response rate for each sent lexical variant of the message text; identifying one or more lexical variants having the best performing measured response rates for each of the lexical vectors; automatically creating on the communications server syntactical variants of the identified best performing lexical variants by rearranging the lexical vectors within the message vector based on one or more position-changing rules; sending a plurality of the syntactical variants of the identified best performing lexical variants to the one or more communications devices, wherein only grammatically-correct syntactical variants are sent; measuring a response rate for each of the sent syntactical variants; and identifying a message text having the highest measured response rate for the sent syntactical variants.