[horde] Call to undefined method Horde_ActiveSync_Request_SendMail::_handError

[Markus Turba]

Since I changed my ubuntu version to 16 I get these glorious  
broadcasts (mind the sarcasm) here and there almost every day I am  
logged into the server saying that the horde installation is missing  
something:

HORDE[19760]: Call to undefined method  
Horde_ActiveSync_Request_SendMail::_handError() [pid 19760 on line 59  
of "/usr/share/php/Horde/ActiveSync/Request/SendMail.php"]

The php logs do not show anything around that time this gets logged  
into syslog. Nginx says the same, just a bit different showing the  
POST request from an AS connection like this:

2016/06/22 14:17:20 [error] 23710#23710: *281651 FastCGI sent in  
stderr: "PHP message: PHP Fatal error:  Call to undefined method  
Horde_ActiveSync_Request_SendMail::_handError() in  
/usr/share/php/Horde/ActiveSync/Request/SendMail.php on line 59" while  
reading response header from upstream, client: x.x.x.x, server:  
xx.xx.xx, request: "POST  
/Microsoft-Server-ActiveSync?User=username&DeviceId=deviceID&DeviceType=iPhone&Cmd=SendMail HTTP/1.1", upstream: "fastcgi://127.0.0.1:9005", host:  
"xxx"

Is this something I can "turn off" because something is wrong in my  
install or is that method just not there (yet) and the error has to be  
endured?

Markus