On 30 Jan 2019, at 18:58, Eli Zaretskii <eliz@gnu.org> wrote:

 Date: Wed, 30 Jan 2019 18:10:29 +0000 (GMT)
 From: john <jpff@codemist.co.uk>
 Cc: 34252@debbugs.gnu.org
 
 This could be due to a kernel/NFS problem but te effect on using rmail for 
 my user-base is a real problem.  The problems with proto being nil in
 rmail-remote-proto-p is clearly wrong and despite your statement it does 
 happen to me on two diffrent computers/users attempting to read mail in 
 emacs via rmail.

If you leave only the one change in the place where Glenn said proto
could be nil, and revert the changes in the other two places, does the
problem still happen to you?

Thanks.