JavaMail: "Domain contains control or whitespace in string" errormessage because of domain with Danish characters

Question

Domains with special danish characters such as æ ø å are now allowed, but I can't force java mail to accept this.

    @Test()
public void testMailAddressWithDanishCharacters1() throws AddressException, UnsupportedEncodingException {
    InternetAddress cAddress = new InternetAddress( "test@testæxample12345123.com", null, "utf-8" );
    System.out.println( cAddress.toString() );
    cAddress.validate();
}

@Test()
public void testMailAddressWithDanishCharacters2() throws AddressException, UnsupportedEncodingException {
    InternetAddress cAddress = new InternetAddress( "test@testæxample12345123.com", false );
    System.out.println( cAddress.toString() );
    cAddress.validate();
}

@Test()
public void testMailAddressWithDanishCharacters3() throws AddressException, UnsupportedEncodingException {
    InternetAddress cAddress = new InternetAddress( "test@testæxample12345123.com", true );
    System.out.println( cAddress.toString() );
    cAddress.validate();
}

All of the tests fail in either the constructor of InternetAddress or in the validate() method. How can I handle these special danish characters in the domain. I bet that other countries have the same issue with their domains vs emails in javamail InternetAddress.

Answer 1

Currently mail servers generally don't accept non-ASCII characters in the local part, only the domain part (following the '@' sign) is supported with IDN.

To encode only the domain part with the java.net.IDN class, i use the following Util.

(Code not tested in production, but it should work)

import java.net.IDN;


public class IDNMailHelper {

    public static String toIdnAddress(String mail) {
        if (mail == null) {
            return null;
        }
        int idx = mail.indexOf('@');
        if (idx < 0) {
            return mail;
        }
        return localPart(mail, idx) + "@" + IDN.toASCII(domain(mail, idx));
    }

    private static String localPart(String mail, int idx) {
        return mail.substring(0, idx);
    }

    private static String domain(String mail, int idx) {
        return mail.substring(idx + 1);
    }

}

Answer 2

Java Mail doesn't support i18n domain names, so you must use the standard rules to escape them using the IDNA rules.