Steps to reproduce:

1. Create maintenance using hostgroup and tag.
2. Create a host with a macro value that should fire a trigger using this macro.

Result:

1. Host created.
2. Event triggered.
3. Message sent (but should not, it should be suppressed by maintenance).

Expected:
Suppression events by tags should work for all hosts in host groups used in maintenance, regardless of whether the hosts were created before or after the maintenance was created.