I am having this same issue as the original poster... However I do use apache instead of nginx... Could I please get the patched file also...

==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.6
- Linux/BSD distribution name and version: Ubuntu 16.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  MySQL
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? Yes
- Related log if you're reporting an issue:
====

Error: OperationalError(1055, "Expression #21 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vmail.sender_relayhost.relayhost' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by")