[exim] filter issue with Japanese characters

Hello,

I have Exim running on a cPanel server with Exim version 4.96.2. I've a
filter for an email address on server which is something like this

```
headers charset "UTF-8"

if not first_delivery and error_message then finish endif

#mytest
if
$header_subject: contains "盛博"
then
deliver "test102@???"
endif
```

The issue is when I send an email from something like google or outlook the
filter is not detecting because of this mail agents send base64 encoded
content and exim not decoding it. If I send an email in plain utf-8 with
Japanese characters in the subject line then the filter works fine.

Is there any way to tell Exim to decode the Japanese characters from the
subject line from base64 encoded content?

any help appreciated.
Thanks
Vaibhav

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