After upgrading an OES2018 server to SP3, LDAP over SSL connections from a GroupWise 18.2.x and earlier system will fail.
In iManager go to: LDAP | LDAP Options | View LDAP Server | select the server | Connections | SSL Configuration | remove tick next to TLSv1.2
Restart eDirectory: ndsmanage stopall && ndsmanage startall
OES2018 SP3 upgrades eDirectory to version 9.2.4. This version of eDirectory, by default, only accepts connections using TLSv1.2. Earlier versions of GroupWise used TLSv1.1. From GroupWise 18.3, GroupWise only uses TLSv1.2. Therefore it is only older, unsupported, versions of GroupWise that are affected by this change in eDirectory security. The best solution is to upgrade your GroupWise system. Alternatively, as a short term work around, you can configure eDirectory to accept less secure connections.