My site is having trouble sending emails out from the forum module.  The emails do get sent to the host account if that person posts a message, but the emails do not get sent to anyone else.  I am getting this error in the Event Viewer:

AssemblyVersion: 04.08.02
PortalID: 9
PortalName: Winterville Football
UserID: 228
UserName: dankoch
ActiveTabID: 493
ActiveTabName: Winterville Football Forum
RawURL: /WintervilleFootballForum/tabid/493/ctl/PostDelete/mid/1240/forumid/1/postid/15/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer: http://www.wintervillefootball.info/WintervilleFootballForum/tabid/493/ctl/PostDelete/mid/1240/forumid/1/postid/15/Default.aspx
UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: afecde17-83d3-4494-873a-eb4da7c46a4d
InnerException: Mailbox unavailable. The server response was: <dan@billclarkhomes.com> No such user here
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.Net.Mail.SmtpTransport.SendMail
StackTrace:
Message: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: <dan@billclarkhomes.com> No such user here at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at DotNetNuke.Services.Mail.Mail.SendMail(String MailFrom, String MailTo, String Cc, String Bcc, String ReplyTo, MailPriority Priority, String Subject, Mailformat Bodyformat, Encoding BodyEncoding, String Body, String[] Attachment, String SMTPServer, String SMTPAuthentication, String SMTPUsername, String SMTPPassword, Boolean SMTPEnableSSL)
Source:
Server Name: VIR117-01

So, if the email address is not in my domain it will throw an error.  Is this something I need to ask my hosting provider about?

Thanks