A method and system for modifying the content of e-mail transmissions based on customization settings determines when an e-mail user has customized an e-mail message and prompts the user to accept or reject automatic modification of the e-mail message text to indicate a particular customization settings. The e-mail program checks the customization settings, then the e-mail program prompts the user if a customization is set for which a text modification can be automatically made. For example, a "cc:" list may be added to the message text in response to the checking detecting a list of copied recipients. The e-mail program may further parse the message text in order to avoid prompting the user to add text associated with a customization for which the user has already made an indication within the message content (message body, subject line, et cetera).