How does CustomMailer check for correct email address syntax?
Internet email addresses supported by CustomMailer can only contain letters, digits, hyphens, periods, underscores, plus signs, ampersands, and a single at sign. Addresses are of the form username@domain.com where username and domain can contain contain letters and digits with intermediate hyphens, periods, underscores, plus signs, and ampersands. All other addresses are regarded as illegal syntax. Strictly speaking, there are other forms of addresses that are possible according to the Internet standards, but they are little-used and in fact don’t work in many standard email programs and mail servers. These include using “IPv4” domain names (e.g., [210.104.76.11]), “quoted” special characters in names (e.g. \m, \036), etc. At present, these are not supported by CustomMailer.
