Login to DirectAdmin Panel of Domain > Go to Account Manager > DNS Management
add CNAME record:
--click Add record
Record Type: CNAME
Name: autodiscover.example.com.
TTL: 600
Value: quickpost.appautodiscover.example.com. 600 CNAME quickpost.app.
Add SRV record:
--click Add record
Record Type: SRV
Name : _autodiscover._tcp
TTL: 600
Priority: 1
Weight: 0
port: 443
Target: autodiscover.example.com._autodiscover._tcp 600 1 0 443 autodiscover.example.com.