[imp] How to flag only one message as "\flagged" with Horde Imap Client library

[Kristers Zariņš]

I'm trying to flag message with the imap flag "\flagged". The problem is
that not only the message I intended to mark gets flagged, but also all
other messages which were sent from the same email address are also flagged.

For example, in my mailbox I have 10 messages from example at host.com. I want
to mark only one of them as "flagged", so I get it's uid and send a
request. But it marks all 10 messages. I want only that one with the
specific uid.

I'm working with gmail account. When flagging messages in gmail's webmail
itself, it marks only one message as intended, so it's not a weird feature
from gmail itself.

The code I'm using is below. What's the problem?

$uids = new Horde_Imap_Client_Ids([1521]);//uid of message I want to mark
as flagged

$options = [
    'uids' => $uids,
    'add' => ['\flagged'],
];

$Imap_Client_Socket->store('INBOX', $options);