Private Sub CommandTo_Click()
    Dim text_to_add As String
    If Len(TextEmailAddress.Text) =  0  Then
        MsgBox "No e-mail address specified for adding to the Recipients list.", vbExclamation + vbOKOnly, "Enter e-mail address"
    ElseIf IsValidEmailAddress(TextEmailAddress.Text) = False Then
        MsgBox "The e-mail address you have entered is not a valid e-mail address.", vbExclamation + vbOKOnly, "Invalid e-mail address"
    ElseIf IsValidEmailName(TextEmailName.Text) = False Then
        MsgBox "The recipient name you have entered can not be used.", vbExclamation + vbOKOnly, "Invalid recipient name"
    Else
        If IsEmailAlreadyInTheList(ListEmailTo, TextEmailAddress.Text) Then
            MsgBox "The e-mail address you have entered is already in the Recipients list and can not be added.", vbExclamation + vbOKOnly, "E-mail address already added"
        Else
            If Len(Trim(TextEmailName.Text)) >  0  Then
                text_to_add = Trim(TextEmailName.Text) & "<" & TextEmailAddress.Text & ">"
            Else
                text_to_add = TextEmailAddress.Text
            End If
            ListEmailTo.ListItems.Add , text_to_add, text_to_add
            ListViewSetItemPicture ListEmailTo, ListEmailTo.ListItems(text_to_add).Index,  0 
        End If
    End If
End Sub

Public Function IsValidEmailAddress(str_email As String) As Boolean
    'проверяет e-mail на валидность
    Dim temp As String
    IsValidEmailAddress = False
    temp = str_email
    If Not (ChNum(temp, "@") =  1 ) Then Exit Function
    If InStr(temp, " ") >  0  Then Exit Function
    If InStr(temp, ";") >  0  Then Exit Function
    If InStr(temp, ",") >  0  Then Exit Function
    If (InStr(temp, "<") >  0 ) Or (InStr(temp, ">") >  0 ) Then Exit Function
    If InStr(temp, Chr( 34 )) >  0  Then Exit Function
    IsValidEmailAddress = True
End Function

Public Function IsValidEmailName(str_name As String) As Boolean
    'проверяет имя получателя на валидность
    Dim temp As String
    IsValidEmailName = False
    temp = str_name
    If InStr(temp, ";") >  0  Then Exit Function
    If InStr(temp, ",") >  0  Then Exit Function
    If (InStr(temp, "<") >  0 ) Or (InStr(temp, ">") >  0 ) Then Exit Function
    If InStr(temp, Chr( 34 )) >  0  Then Exit Function
    IsValidEmailName = True
End Function

Public Function IsEmailAlreadyInTheList(the_listview As ComctlLib.ListView, str_email As String) As Boolean
    Dim the_email_in_list As String
    Dim i As Integer
    For i =  1  To the_listview.ListItems.Count
        the_email_in_list = the_listview.ListItems(i).Text
        'вычленение email, если указано имя
        If InStr(the_email_in_list, "<") >  0  Then
            the_email_in_list = _
              Trim(Right(the_email_in_list, Len(the_email_in_list) - InStr(the_email_in_list, "<")))
        End If
        If InStr(the_email_in_list, ">") >  0  Then
            the_email_in_list = _
              Trim(Left(the_email_in_list, InStr(the_email_in_list, ">") -  1 ))
        End If
        'сравнение
        If the_email_in_list = str_email Then
            IsEmailAlreadyInTheList = True
            Exit Function
        End If
    Next i
    IsEmailAlreadyInTheList = False
End Function

Private Sub TextBox_Change()
    'защита от ввода символа перевода каретки(ибо этот символ суть разделитель)
    If InStr(TextBox.Text, Chr( 10 )) >  0  Then
        TextBox.Text = tochkaSTR(TextBox.Text, Chr( 10 ), "")
    End If
    If InStr(TextBox.Text, Chr( 13 )) >  0  Then
        TextBox.Text = tochkaSTR(TextBox.Text, Chr( 13 ), "")
    End If
End Sub