Comment 2 for bug 1831321

I attached an export from our old server (via config_list -o). In my export the encoding looks OK. On our new server I had to fix the description from:
description = "<D6>ffentliche Supportliste"
(thats the way less displays the export on the new machine)
to:
description = "Öffentliche Supportliste"

hexdump of the export on the new machine:
00000930 64 65 6e 2e 0a 64 65 73 63 72 69 70 74 69 6f 6e |den..description|
00000940 20 3d 20 22 d6 66 66 65 6e 74 6c 69 63 68 65 20 | = ".ffentliche |
00000950 53 75 70 70 6f 72 74 6c 69 73 74 65 22 0a 0a 23 |Supportliste"..#|

preferred_language on the new system stayed the same through the ex-/import:
preferred_language = 'de'

It seems that the old setup was migrated using rsync. I was able to reproduce the problem by syncing only /var/lib/mailman/lists/helpdesk/config.pck from the old machine. This broke the encoding, and lead to the following mail header:
List-Id: helpdesk.csn.tu-chemnitz.de

We are currently using Mailman version 2.1.23 under Debian 9.9. The old machine ran with Ubuntu 12.04.5 LTS and Mailman version 2.1.14.