Thanks @alento.
In fact, it has been filed already. And from the pull-request I found what seems to have made it finally work again as expected.
In short manually adding the “fastcgi_read_timeout 300;” statement to my nginx.conf file made all the difference. Searches now can sail past the 60 second timeout value and return full results.
Also note, I reverted a lot of the other changes to timeouts (in /etc/php/7.2/cli and fpm) made as testing has proven these are not necessary. They are now back at their defaults.
Only two changes are needed to realise the fix to the problem.
The first is to change the IMAP timeout in:
/usr/local/lib/roundcubemail/config/config.inc.php
$config[‘imap_timeout’] = 300;
and the second change is to add “fastcgi_read_timeout 300;” to
/etc/nginx/nginx.conf
http {
##
# Basic Settings
##
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;
fastcgi_read_timeout 300;
# server_names_hash_bucket_size 64;
server_names_hash_bucket_size 128;
# server_name_in_redirect off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
##
# SSL Settings
##
Here is the source pull request where I found those fixes.
I just searched 60,000+ emails for the word “the” (thinking that would be most abusive) and it works perfectly now.
@mcl I would be curious if this fixes your same / similar problem.
I hope it helps you like it helped me. I can now close my wife’s trouble ticket.