`LIST` returns wrong UTF-7 encoded mailbox with `&` in its name

[Vovan-VE]

1. Yandex mail
2. A mailbox with & in its name.
3. IMAP LIST command.

An example response line from LIST command for a mailbox:

* LIST (\HasNoChildren \Marked) "|" "INBOX"

With example mailbox name Абв&где:

Expected UTF-7 mailbox name:

&BBAEMQQy-&-&BDMENAQ1-

Actual UTF-7 mailbox name:

&BBAEMQQyACYEMwQ0BDU-

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UPD: The issue happens in some unknown edge cases, rather then with every & anywhere.

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RFC 9051: A.1

[Vovan-VE]

The issue happens in some unknown edge cases, rather then with every & anywhere. (issue updated)