Question

I search the eror But I found nothing. My Mail setting is well form. Is there any idea what couse of this exception?

Mail Configuration

<add key="SMTPFrom" value="[e-mail]" />
<add key="SMTPReplyTo" value="[e-mail]"/>
<add key="SMTPCredentialUserName" value="company_mailer_system"/>
<add key="SMTPCredentialPassword" value="password"/>
<add key="SMTPHost" value="hostUrl" />

I add some mailaddress myMail.To.Add(to) and to contains mail addresses splited by ;

Answer 1

I think you need to split the addresses in to and add them one at a time

string[] addrs = to.Split(";");
foreach (string addr in addrs) {
    myMail.To.Add(addr);
}