1. A non-transitory computer-readable storage medium including instructions that when executed by at least one processor implement a computer system comprising: a condition engine configured to determine one or more conditions associated with data for each of a plurality of target recipients, the message including a subject line and a separate body portion, the one or more conditions being received from a user different than the plurality of target recipients; a text handler configured to-receive text for inclusion in the subject line, the text including at least one of conditional text dependent upon an evaluation of the one or more conditions for inclusion in the subject line or universal text for inclusion in the subject line independent of the evaluation of the one or more conditions; a variable handler configured to determine one or more variables for inclusion with the subject line, the one or more variables including at least one of conditional variables dependent upon the evaluation of the one or more conditions for inclusion with the subject line or universal variables for inclusion with the subject line independent of the evaluation of the one or more conditions; a condition evaluator configured to perform the evaluation of the one or more conditions and determine which of the conditional text is included in and which of the conditional variables are included with the subject line based on the evaluation; an execution service configured to determine one or more values, for each of the one or more target recipients, corresponding to each of the universal variables and the conditional variables for inclusion with the subject line; and an assembler configured to personalize the subject line of the message for each of the plurality of target recipients based on the evaluation of the one or more conditions, the subject line including the universal text, the one or more values corresponding to the universal variables, and, as determined based on the evaluation, the determined conditional text for inclusion in and the one or more values corresponding to the determined conditional variables for inclusion with the subject line, the conditional text including a word in a first language for a first target recipient of the plurality of target recipients, the conditional text including a word in a second language different than the first language for a second target recipient of the plurality of target recipients different than the first target recipient.