I had the same problem (DNN 4.05.03). Here is a less than optimal, quick and dirty fix which should work until the new forums are released.
In ForumUtils.vb
Public Shared Function SendPMMail...
'If Not Len(_portalSettings.HostSettings("SMTPServer")) = 0 Then
' SmtpMail.SmtpServer = CType(_portalSettings.HostSettings("SMTPServer"), String)
'End If
forumMail.To = PMRecipientUser.Email
'SmtpMail.Send(forumMail)
Dim smtpServer As String = Convert.ToString(_portalSettings.HostSettings("SMTPServer"))
Dim smtpAuthentication As String = Convert.ToString(_portalSettings.HostSettings("SMTPAuthentication"))
Dim smtpUserName As String = Convert.ToString(_portalSettings.HostSettings("SMTPUsername"))
Dim smtpUserPassword As String = Convert.ToString(_portalSettings.HostSettings("SMTPPassword"))
'Dim nfo As UserInfo = UserController.GetCurrentUserInfo()
'forumMail.To = nfo.Email
DotNetNuke.Services.Mail.Mail.SendMail(forumMail.From, "noreply@YourCompany.com", forumMail.Bcc, forumMail.Subject, _
forumMail.Body, "", forumMail.BodyFormat.ToString(), smtpServer, smtpAuthentication, _
smtpUserName, smtpUserPassword)
Public Shared Function SendForumMail...
'If Not Len(_portalSettings.HostSettings("SMTPServer")) = 0 Then
' SmtpMail.SmtpServer = CType(_portalSettings.HostSettings("SMTPServer"), String)
'End If
Dim distributionlist As Object
For Each distributionlist In forumMail.DistributionLists
Dim strDistribution As String = CType(distributionlist, String)
forumMail.Bcc = strDistribution
Try
'CP - COMEBACK - Change to per user email preferences
forumMail.BodyEncoding = System.Text.Encoding.UTF8
'SmtpMail.Send(forumMail)
Dim smtpServer As String = Convert.ToString(_portalSettings.HostSettings("SMTPServer"))
Dim smtpAuthentication As String = Convert.ToString(_portalSettings.HostSettings("SMTPAuthentication"))
Dim smtpUserName As String = Convert.ToString(_portalSettings.HostSettings("SMTPUsername"))
Dim smtpUserPassword As String = Convert.ToString(_portalSettings.HostSettings("SMTPPassword"))
Dim nfo As UserInfo = UserController.GetCurrentUserInfo()
forumMail.To = nfo.Email
DotNetNuke.Services.Mail.Mail.SendMail(forumMail.From, forumMail.To, forumMail.Bcc, forumMail.Subject, _
forumMail.Body, "", forumMail.BodyFormat.ToString(), _
smtpServer, smtpAuthentication, smtpUserName, smtpUserPassword)
Catch exc As System.Exception
LogException(exc)
End Try
Next
This hack may help for for the interim.