Please consider Mailbox before adding attachments

Where I work, the standard attachment size is becoming around 3MB and we are only allocated 512MB of Outlook storage space. Rather than my email signature reading "Please consider the environment before printing this email", would it be unprofessional to change it to something like "Please consider Mailbox before adding attachments"? What's a better way of phrasing this if I were to use it in my email signature?