The problem in the names of attachments in Cyrillic

[don_kikhot]

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Hello, there are problems with investments in the Cyrillic and at what it seems only with messages from thunderbird,
Help please understand

Roundcube Webmail 1.3.4
Ubuntu 16.04

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PHP 7.0.22-0ubuntu0.16.04.1 (cli) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
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[alec]

This is more likely a problem with your IMAP server. Enable imap_debug to see what's returned by the server.