[horde] Sending HTTP 401 Unauthorized header response

[Arjen de Korte]

Possibly more log spam:

2019-01-04T13:23:44+01:00 ERR: horde Sending HTTP 401 Unauthorized  
header response. [pid 1949 on line 126 of  
"/usr/share/php7/PEAR/Horde/Rpc/ActiveSync.php"]

Dumping $serverVars just a few lines before this line, it looks like  
the client attempts to authenticate with type "Bearer" but there is no  
token. I also see requests where the same client is using Basic  
authentication with a base64 encoded username and password, which  
works fine. The client in question is the built-in Windows 10 Mail and  
synchronizes as usual.

I've removed the account and recreated it, but the problem remains.