[imp] Adding attachments under Windows does not work after upgrade to IMP 6.1.8

[Jens Grüntjes]

Hello list,

after an update yesterdays, today I can not upload attachments bigger  
than about 140 kBytes in a Windows environment (files > 1 MByte  
definitely don't work). It does not matter which browser I choose, it  
doesn't work with either Firefox 30, IE 11 or Chrome 35.0.1916.153.  
When I try to attach the same files in a Linux environment it works  
with Firefox 30 at least.

By the way, if I add the attachment with IE 11, the "open file"  
dialogue shows up again immediately after adding the file. No idea  
what that is.

If the file is correctly attached I see in the horde log file an entry  
like: '"file.xls" added as an attachment' (in my German environment it  
reads '"file.xls" als Anhang hinzugefügt.' If I try to attach the file  
within a Windows browser nothing appears in the log file (log level is  
DEBUG).

I'm using the latest stable PEAR packages (just upgraded), which is

webmail 5.1.5
imp 6.1.8

The server runs on Debian Wheezy

Greetings
Jens