How to fix exception thrown when sending mail message to multiple recipients?

Question

In the code snippet below, I'm getting a FormatException on 'this.Recipients'. More specifically, the message is "An invalid character was found in the mail header: ';'".

Recipients is a string of three email addresses separated by semicolons (the ';' character). The list of recipients is read from an app.config and the data is making it into the Recipients variable.

How can I be getting this error when multiple recipients should be separated by a semicolon? Any suggestions? As always, thanks for your help!

public bool Send()
{
    MailMessage mailMsg = 
       new MailMessage(this.Sender, this.Recipients, this.Subject, this.Message);

    SmtpClient smtpServer = new SmtpClient(SMTP);
    smtpServer.DeliveryMethod = SmtpDeliveryMethod.Network;

Edit #1 - This says use a semicolon.

Answer 1

I can't see anything in the MailMessage constructor documentation to suggest you can specify multiple recipients like that. I suggest you create the MailMessage object and then add each email address separately.

Note that the MailAddressCollection.Add method is documented to accept comma-separated addresses... so it's possible that that would work in the constructor too.

Answer 2

You have to use the .Add method to add these addresses. Here is some sample code that I use:

string[] toAddressList = toAddress.Split(';');

//Loads the To address field
foreach (string address in toAddressList)
{
    if (address.Length > 0)
    {
        mail.To.Add(address);
    }
}

Answer 3

Reviving this from the dead, if you separate the recipient email addresses by a comma, it will work.

this.Recipients = "[email protected], [email protected]";

var mailMsg = new MailMessage(this.Sender, this.Recipients, this.Subject, this.Message);
SmtpClient smtpServer = new SmtpClient(SMTP);
smtpServer.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpServer.Send(mailMsg);