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Re: PDF email attachments

Firefox Extended Support Release (ESR) seems a bit overkill for a domestic environment - or is this a commercial environment (which is fine, by the way).  Since FF ESR is designed for a particular kind of user, this might be a contributory factor...
Firefox Extended Support Release (ESR) seems a bit overkill for a domestic environment - or is this a commercial environment (which is fine, by the way).  Since FF ESR is designed for a particular kind of user, this might be a contributory factor to your problems. 

You say you are using a Linux Debian system. 
Can you provide a bit more information about your system?  Like which Debian-based OS (and version) you are using (Ubuntu, Mint.....) or is it Debian itself?  This might help people to adv...