Question

I’m trying to talk to Fax server software using an email. The fax server will accept formatted SMTP mails and covert them to faxes and send them to the fax number defined in the to address. This has been manually tested by sending an email from Outlook via the same server.

Here’s my problem – System.Net.Mail is throwing an
System.FormatException: The specified string is not in the form required for an e-mail address. exception due to the format of the email address that I am trying to send to

Is there any way I can turn off/change this validation because the email address may not be RFC compliant but it will work if the email gets sent

i.e. I want to send to [RFax:User@/FN=0123456789] including the square brackets

You can send to this as an e-mail address in Outlook

Cheers
Chris

EDIT

This is a cut-down version of the class I’m using to bypass the validation. There are two ways of doing it – one by overriding the constructor and setting the internal attribute directly, the other using an internal constructor. They have slightly different effects if there are spaces in the email address

using System;
using System.Reflection;

namespace Mail
{
    public class UnverifiedEmailAddress : System.Net.Mail.MailAddress
    {
        /// <summary>
    /// Constructor to bypass the validation of MailAddress
    /// </summary>
    /// <param name="address">Email address to create</param>
    public UnverifiedEmailAddress(string address)
        : base("a@a")
    {
        FieldInfo field = typeof(System.Net.Mail.MailAddress).GetField("address", BindingFlags.Instance | BindingFlags.NonPublic);
        field.SetValue(this, address);
    }

    /// <summary>
    /// Static method to create an unverifed email address bypassing the address validation
    /// </summary>
    /// <param name="address">Email address to create</param>
    /// <param name="displayName">Display name for email address</param>
    /// <returns></returns>
    private static System.Net.Mail.MailAddress GetUnverifiedEmailAddress(string address, string displayName)
    {
            ConstructorInfo cons = typeof(System.Net.Mail.MailAddress).GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic,
                                                                null,
                                                                new Type[] { typeof(string), typeof(string), typeof(UInt32) },
                                                                null);

            object obj = cons.Invoke(new object[] { address, displayName, UInt32.MinValue });
            System.Net.Mail.MailAddress toAddressObj = (System.Net.Mail.MailAddress)obj;
            return toAddressObj;
        }
    }
}

Answer 1

No, you cannot turn that validation off.

EDIT:

After looking in to this a little bit it seems as if the following code snippet would be a feasible workaround:

ConstructorInfo ctor = typeof(MailAddress).GetConstructor(
    BindingFlags.NonPublic | BindingFlags.Instance, null,
    new Type[] { typeof(string), typeof(string), typeof(string) }, null);

MailMessage msg = new MailMessage
{
    To = { (MailAddress)ctor.Invoke(new object[] { null, "[RFax:User", "/FN=0123456789]" }) }
};

There are two tricks here. The first one is to use the internal MailAddress constructor that doesn’t parse/validate the supplied address.

The second trick is to split “fax address” on the @-sign and pass it as two parts (user and domain). This is needed because the SMTP To-header is later written by the framework using the MailAddress.Address property, and that property returns user + @ + domain.