How to search for a specific e-mail message in IMAP mailbox?

Question

How can I retrieve a specific e-mail based on a certain text contained in the message ? For example how Gmail search works. If you search for a specific text, which is in the e-mail, then the Gmail will retrieve the message that is associated with the text. Preferably without any looping.

Answer 1

You're looking for the SearchMailBox method. Here's a simple example expecting that you have the IMAP client (in this case, the IMAPClient variable of the TIdIMAP4 type) already connected to the Gmail server. For those looking for how to do so, take a look for instance at this post and put this code inside the try..finally block near IMAPClient.Connect and IMAPClient.Disconnect.

var
  // in this example is not shown how to connect to Gmail IMAP server but
  // it's expected that the IMAPClient object is already connected there
  IMAPClient: TIdIMAP4;

procedure TForm1.Button1Click(Sender: TObject);
var
  I: Integer;
  MsgObject: TIdMessage;
  SearchInfo: array of TIdIMAP4SearchRec;
begin
  // if the mailbox selection succeed, then...
  if IMAPClient.SelectMailBox('INBOX') then
  begin
    // set length of the search criteria to 1
    SetLength(SearchInfo, 1);
    // the SearchKey set to skBody means to search only in message body texts
    // for more options and explanation, see comments at the TIdIMAP4SearchKey
    // enumeration in the IdIMAP4.pas unit
    SearchInfo[0].SearchKey := skBody;
    // term you want to search
    SearchInfo[0].Text := 'Search term';

    // if the search in the selected mailbox succeed, then...
    if IMAPClient.SearchMailBox(SearchInfo) then
    begin
      // iterate the search results
      for I := 0 to High(IMAPClient.MailBox.SearchResult) do
      begin
        // make an instance of the message object
        MsgObject := TIdMessage.Create(nil);
        try
          // try to retrieve currently iterated message from search results
          // and if this succeed you can work with the MsgObject
          if IMAPClient.Retrieve(IMAPClient.MailBox.SearchResult[I], 
            MsgObject) then
          begin
            // here you have retrieved message in the MsgObject variable, so
            // let's do what what you need with the >> MsgObject <<
          end;
        finally
          MsgObject.Free;
        end;
      end;
    end;
  end;
end;

Here's the quick implementation of the IMAP search for UTF-8 charset. It uses interposed class due to protected ParseSearchResult method:

type
  TBasicSearchKey = (bskBcc, bskBody, bskCc, bskFrom, bskHeader, bskKeyword,
    bskSubject, bskText, bskTo);
const
  IMAPSearchKeys: array [TBasicSearchKey] of string = ('BCC', 'BODY', 'CC',
    'FROM', 'HEADER', 'KEYWORD', 'SUBJECT', 'TEXT', 'TO');
type
  TIdIMAP4 = class(IdIMAP4.TIdIMAP4)
  public
    function SearchMailBoxUTF8(const ASearchText: string;
      ASearchKey: TBasicSearchKey): Boolean;
  end;

implementation

{ TIdIMAP4 }

function TIdIMAP4.SearchMailBoxUTF8(const ASearchText: string;
  ASearchKey: TBasicSearchKey): Boolean;
var
  SearchText: RawByteString;
begin
  Result := False;
  CheckConnectionState(csSelected);

  SearchText := UTF8Encode(ASearchText);
  SendCmd(Format('SEARCH CHARSET UTF-8 %s {%d}', [IMAPSearchKeys[ASearchKey],
    Length(SearchText)]), ['SEARCH']);
  if LastCmdResult.Code = IMAP_CONT then
    IOHandler.WriteLn(SearchText, TEncoding.UTF8);

  if GetInternalResponse(LastCmdCounter, ['SEARCH'], False) = IMAP_OK then
  begin
    ParseSearchResult(FMailBox, LastCmdResult.Text);
    Result := True;
  end;
end;

And the usage:

procedure TForm1.Button1Click(Sender: TObject);
var
  I: Integer;
  MsgObject: TIdMessage;
begin
  if IMAPClient.SelectMailBox('INBOX') and
    IMAPClient.SearchMailBoxUTF8('Search term', bskText) then
  begin
    for I := 0 to High(IMAPClient.MailBox.SearchResult) do
    begin
      MsgObject := TIdMessage.Create(nil);
      try
        if IMAPClient.Retrieve(IMAPClient.MailBox.SearchResult[I],
          MsgObject) then
        begin
          // here you have retrieved message in the MsgObject variable, so
          // let's do what what you need with the >> MsgObject <<
        end;
      finally
        MsgObject.Free;
      end;
    end;
  end;
end;