Yes I issued 'pear install horde/horde_lz4', it downloaded and 
compiled and added the .so to my extensions directory.  I then loaded 
it via my php.ini file.

I had manually purged the horde cache directory by simply deleting all 
files, I even deleted files in my static directory, then restarted 
Apache.  I purge cache on the client end also.

I just tried all of this again and this time used your suggested 
horde-clear-cache command.  I see the same outcome.

For now, I will exclude horde_lz4 module.  I can't say why I am seeing 
this behavior.  I am happy to test more on my end if it is of any 
value for you.  If not, please close this ticket and I will just use 
lzf by default and no load horde_lz4.   Thanks.

Cannot reproduce. Are you sure you didn't enable/install horde_lz4 
*while* you were logged in? This won't work, because it's used to 
compress the session data. It may also be use while compressing the 
cache, so you can try running horde-clear-cache too.

Hi,
Upgrading to Horde Groupware 5.2.22, IMP 6.2.21 on a SLES 12-SP3 
system with PHP 5.5.

If I install the PEAR package horde_lz4-1.0.10 and load via 
extension=horde_lz4.so in the PHP.INI, as recommended by the 
installation manual, I notice that the IMP application fails to work.   
After login, I see these errors:

ERR: HORDE [imp] IMP is marked as authenticated, but no credentials 
can be found in the session. [pid 13175 on line 628 of 
"/data/www/horde/imp/lib/Imap.php"]

I have configured Horde to authenticate against my IMAP server.

If I load the PEAR lzf module, all works fine.  If I load both lzf and 
horde_lz4, IMP gets the error.  Everything else works fine when IMP is 
not working (with lz4 loaded).

I have removed horde_lz4 for now.

Thanks