some background information: EPIM file is a Firebird database. There are 2 flavours of Firebird: EPIm Desktop/Portable uses Embedded Firebird Server (which does not need a separate server installation), while Network version uses full Firebird server.
So, Embedded version can not use databases on network shares for a number of reasons:http://www.firebirdsql.org/manual/ufb-cs-embedded.html
"The embedded server has no facility to accept any network connections. Only true local access is possible, with a connect string that doesn't contain a host name (not even localhost)."
"When an application loads the embedded server, the server operates in the application (and therefore the user's) security context. This means that the embedded server will only be able to access database files that the user could access directly through the operating system. Giving an untrusted user access to install programs on a secure server is bad news in any case, but provided you have specified appropriate file permissions on secure databases, the embedded server itself is no threat. "
So what you can do:
- use Desktop/Portable version, without possibility to reach your EPIM files on NAS
- try to install Firebird server on your NAS. There lots of builds of Firebird for Linux: http://www.firebirdsql.org/en/firebird-2-5-1/
- install Firebird server on some other machine (not NAS)
The main thing, that if you use Network version, server must be installed on the same machine where EPIM database files are. Then you can reach your files through server from whenever you want, even over the Internet (outside local network).