Subject decoding error results in unusable envelope

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My testing Imapfolder contains a message with this subject:

Subject: =?UTF-8?Q?Fwd=3A_Re=3A_=5BS4f-koordinationsteam=5D_Leitfaden_f?==?UTF-8?Q?=C3=BCr=2C_Publikationen_in_der_Reihe=2C_=E2=80=9EDiskussionsbeit?==?UTF-8?B?csOkZ2UgZGVyIFM0RuKAnCwgVmVyc2lvbiAwLjk5MywgRGV1dHNjaCwgU3RhbmQ6?==?UTF-8?Q?_21=2E_September_2023?=

By fetching messages envelope (e.g. .fetchMessagesNextPage) this Message prints debug errors that it is unable to encode subject, but does not throw Exception.

But the envelope of this MimeMessage is null, so nothing can be retrieved here.

My guess for the encoding error is, that this subject contains mixed encoding types (Q and B). But eg Thunderbird or ar more basic tool like https://dogmamix.com/MimeHeadersDecoder/ encodes it without error.

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Forgot the Version: enough_mail 2.1.7

The problem is getting more urgent, because in addition to the encoding error the following happens:

When I am requesting e.g. with this Code
List<MimeMessage> msgPage = await currentMailClient!.fetchMessagesNextPage( _currentMessageSequence!, fetchPreference: FetchPreference.envelope, );
Not only the Mail with the encoding error, although the email in the order following these is not retrieved.
So requesting Email listing form the IMAP Server ist unreliable because it could always happen, and as a result there are missing emails.

The Problem always occurs when ENVELOPE is requested indepentent if MailClient or ImapClient is used.