There are multiple synonyms for the phrase "write away for," which means to send a request or application for something by mail. One alternative is "mail in," as in "I'm going to mail in my application for the scholarship." Another option is "request by mail," as in "I'm going to request the brochure by mail." Additionally, one could use the term "send for," as in "I'm going to send for the catalog." Another synonym could be "apply by post," as in "I'm going to apply for the job by post." Whatever the synonym used, it is important to remember that this method of communication may take longer than other electronic means.