请兄弟们帮忙解决邮件发出的问题 ( 积分: 50 )

各位兄弟，我在做一个发出邮件的程序，其目的是将一份邮件按照我要求的份数自动发到固定的邮箱，其中邮箱地址和邮件发出的份数都是在界面中设置的，我用的是163的邮箱，要发到sohu的邮箱。
现在出现的问题是，我设定发送10份邮件到一个邮箱，每次发送6个邮件后，系统就报错，大家帮我看看这是什么原因。

下面是全部代码：
const BaseTable:string='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

var
Form1: TForm1;
AuthSucc:boolean;// 是否需要密码验证
function DecodeBase64(Source:string):string; //解码函数
function FindInTable(CSource:char):integer; //
function EncodeBase64(Source:string):string; //编码函数
implementation
{$R *.DFM}

//
function FindInTable(CSource:char):integer;
begin
result:=Pos(string(CSource),BaseTable)-1;
end;
////

function DecodeBase64(Source:string):string;
var
SrcLen,Times,i:integer;
x1,x2,x3,x4,xt:byte;
begin
result:='';
SrcLen:=Length(Source);
Times:=SrcLen div 4;
for i:=0 to Times-1 do
begin
x1:=FindInTable(Source[1+i*4]);
x2:=FindInTable(Source[2+i*4]);
x3:=FindInTable(Source[3+i*4]);
x4:=FindInTable(Source[4+i*4]);
x1:=x1 shl 2;
xt:=x2 shr 4;
x1:=x1 or xt;
x2:=x2 shl 4;
result:=result+chr(x1);
if x3= 64 then break;
xt:=x3 shr 2;
x2:=x2 or xt;
x3:=x3 shl 6;
result:=result+chr(x2);
if x4=64 then break;
x3:=x3 or x4;
result:=result+chr(x3);
end;
end;
/////

function EncodeBase64(Source:string):string;
var
Times,LenSrc,i:integer;
x1,x2,x3,x4:char;
xt:byte;
begin

result:='';
LenSrc:=length(Source);
if LenSrc mod 3 =0 then
Times:=LenSrc div 3
else
Times:=LenSrc div 3 + 1;
for i:=0 to times-1 do
begin
if LenSrc >= (3+i*3) then
begin
x1:=BaseTable[(ord(Source[1+i*3]) shr 2)+1];
xt:=(ord(Source[1+i*3]) shl 4) and 48;
xt:=xt or (ord(Source[2+i*3]) shr 4);
x2:=BaseTable[xt+1];
xt:=(Ord(Source[2+i*3]) shl 2) and 60;
xt:=xt or (ord(Source[3+i*3]) shr 6);
x3:=BaseTable[xt+1];
xt:=(ord(Source[3+i*3]) and 63);
x4:=BaseTable[xt+1];
end
else if LenSrc>=(2+i*3) then
begin
x1:=BaseTable[(ord(Source[1+i*3]) shr 2)+1];
xt:=(ord(Source[1+i*3]) shl 4) and 48;
xt:=xt or (ord(Source[2+i*3]) shr 4);
x2:=BaseTable[xt+1];
xt:=(ord(Source[2+i*3]) shl 2) and 60;
x3:=BaseTable[xt+1];
x4:='=';
end else
begin
x1:=BaseTable[(ord(Source[1+i*3]) shr 2)+1];
xt:=(ord(Source[1+i*3]) shl 4) and 48;
x2:=BaseTable[xt+1];
x3:='=';
x4:='=';
end;
result:=result+x1+x2+x3+x4;
end;
end;

//////////
procedure TForm1.Button1Click(Sender: TObject);
//var MailTo,MailBody:TStringList;
var s74:integer; //发出邮件的份数
p74:integer; //用于判断是否达到邮件份数的判断条件
begin
s74:=strtoint(edit7.Text);
p74:=0;
while p74<s74 do //用于判断是否达到要发的邮件份数
begin
Nmsmtp1.Host :=Edit1.Text;
nmsmtp1.Port :=25;
nmsmtp1.UserID :=Edit2.Text;//发信人的用户名，必须是真实的
nmsmtp1.ReportLevel :=1;
Nmsmtp1.TimeOut :=1000;
if p74=0 then
nmsmtp1.Connect ; ///连接

if AuthSucc=true then ////验证成功
begin
nmsmtp1.PostMessage.FromAddress:=Edit4.Text; //发信人的电子邮件地址
nmsmtp1.PostMessage.ToAddress.Text :=Edit5.Text;
nmsmtp1.PostMessage.Body.Text:=Memo1.Text;
nmsmtp1.PostMessage.Subject :=Edit6.Text;
nmsmtp1.SendMail;
end;
p74:=p74+1;
end;
end;

procedure TForm1.NMSMTP1Connect(Sender: TObject);
begin
//////连接成功，下面用户认证过程
StatusBar1.SimpleText:=nmsmtp1.Status;
if nmsmtp1.ReplyNumber = 250 then
StatusBar1.SimpleText:=nmsmtp1.Transaction('auth login'); //开始认证
if nmsmtp1.ReplyNumber =334 then //返回值为334，让你输入用BASE64编码后的用户名
StatusBar1.SimpleText:=nmsmtp1.Transaction(EncodeBase64(Edit2.Text));
if nmsmtp1.ReplyNumber =334 then // 返回值为334，让你输入用BASE64编码后的用户密码
StatusBar1.SimpleText:=nmsmtp1.Transaction(EncodeBase64(Edit3.Text));
if nmsmtp1.ReplyNumber =235 then
begin
StatusBar1.SimpleText:='successful';
AuthSucc:=true;
end;
end;

procedure TForm1.NMSMTP1InvalidHost(var Handled: Boolean);
begin
StatusBar1.SimpleText :='Invalid Host';
end;
procedure TForm1.NMSMTP1ConnectionFailed(Sender: TObject);
begin
StatusBar1.SimpleText :='connect failed';
end;
procedure TForm1.NMSMTP1Status(Sender: TComponent; Status: String);
begin
StatusBar1.SimpleText :=nmsmtp1.Status ;
end;
procedure TForm1.NMSMTP1SendStart(Sender: TObject);
begin
StatusBar1.SimpleText :='start send';
end;
procedure TForm1.NMSMTP1Success(Sender: TObject);
begin
StatusBar1.SimpleText:='send success!';
end;