使用Indy 10和DELPHI评估电子邮件

您还需要考虑TIdMessage.ContentType,因为HTML电子邮件可能不是MIME编码的,因此根本不使用TIdMessage.MessageParts`集合.

最后,循环需要使用MessageParts.Count属性而不是MessageParts.AttachmentsCount属性.

试试这个：

function HTMLFromMsg(aMsg: TIdMessage): TStrings; 
var
  i: Integer; 
  Part: TIdMessagePart;
begin
  Result := nil;
  if IsHeaderMediaType(aMsg.ContentType,'text/html') then
  begin
    Result := aMsg.Body;
    Exit;
  end;
  for i := 0 to aMsg.MessageParts.Count-1 do
  begin
    Part := aMsg.MessageParts.Items[i];
    if (Part is TIdText) and IsHeaderMediaType(Part.ContentType,'text/html') then
    begin
      Result := TIdText(Part).Body;
      Exit;
    end;
  end; 
end;

话虽如此,从技术上讲,这不是处理MIME的正确方法.正式地说,符合标准的读者应该通过MIME部分向后循环,因为它们从最简单的形式向下排序到最复杂的形式.因此,您需要向后循环,将MIME嵌套考虑在内,寻找您支持的最复杂的表单.更像这样的东西(未经测试)：

procedure DisplayPlainText(Body: TStrings);
begin
  // display plain text as needed...
end;

procedure DisplayHTML(Body: TStrings);
begin
  // display html as needed...
end;

procedure DisplayMultiPartAlternative(aMsg: TIdMessage; aParentIndex,aLastIndex: Integer);
var
  Part: TIdMessagePart;
  i: Integer:
begin
  for i := aLastIndex-1 downto aParentIndex+1 do
  begin
    Part := aMsg.MessageParts.Items[i];
    if (Part.ParentPart = aParentIndex) and (Part is TIdText) then
    begin
      if IsHeaderMediaType(Part.ContentType,'text/html') then
      begin
        DisplayHTML(TIdText(Part).Body);
        Exit;
      end;
      if IsHeaderMediaType(Part.ContentType,'text/plain') then
      begin
        DisplayPlain(TIdText(Part).Body);
        Exit;
      end;
    end;
  end;
  // nothing supported to display...
end;

procedure DisplayMultiPartMixed(aMsg: TIdMessage; aParentIndex,aLastIndex: Integer);
var
  Part: TIdMessagePart;
  i: Integer;
begin
  for i := aLastIndex-1 downto aParentIndex+1 do
  begin
    Part := aMsg.MessageParts.Items[i];
    if (Part.ParentPart = aParentIndex) and (Part is TIdText) then
    begin
      if IsHeaderMediaType(Part.ContentType,'multipart/alternative') then
      begin
        DisplayMultiPartAlternative(aMsg,ParentPart.Index,aLastIndex);
        Exit;
      end;
      if IsHeaderMediaType(ParentPart.ContentType,'text/plain') then
      begin
        DisplayHTML(TIdText(Part).Body);
        Exit;
      end;
      aLastIndex := i;
    end;
    // nothing supported to display...
  end;


procedure DisplayMsg(aMsg: TIdMessage); 
var
  ContentType: string;
begin
  ContentType := ExtractHeaderMediaType(aMsg.ContentType);
  case PosInStrArray(ContentType,['multipart/mixed','multipart/alternative','text/html','text/plain'],False) of
    0: begin
      DisplayMultiPartAlternative(aMsg,-1,aMsg.MessageParts.Count);
      Exit;
    end;
    1: begin
      DisplayMultiPartMixed(aMsg,aMsg.MessageParts.Count);
      Exit;
    end;
    2: begin
      DisplayHTML(aMsg.Body);
      Exit;
    end;
    3: begin
      DisplayPlainText(aMsg.Body);
      Exit;
    end;
  else
    // nothing supported to display...
  end;
end;