Should be: fööbär
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Subject: =?UTF8?B?WW91ciByZWNlbnQgcHVyY2hhc2U=?=
Date: Tue,  4 Feb 2020 10:23:08 +0000
From: admin@example.com
To: frank@example.com

This is a multi-part message in MIME format.

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text: fööbär

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<h1>fööbär</h1>

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