If you only have a single domain in Active Directory (or if multiple domains, there is a trusted relationship between them), then all you have to do is add the Retain server to the domain to which the workstations belong that are running Outlook. Retain connects to EWS through autodiscover just like Outlook.
However, some customers have multiple Active Directory domains and trusts do not exist for various reasons. In such cases, SRV records are required.
Microsoft has a detailed article about the SRV record: Setting up a DNS SRV record
In simple terms:
- Go to the DNS Manager
- Expand Forward Lookup Zones
- Locate and right-click on the external DNS zone and choose Other New Records
- Click Service Location (SRV) and enter:
Port Number: 443
Host: [your mail host, e.g. mail.gwava.net, usually the AD domain forest found in AD Domains and Trusts on the MS AD server]
- Click OK
The Microsoft autodiscover library in Retain expects a URL along the lines of https://autodiscover.[your domain]/Autodiscover/Autodiscover.xml (e.g., https://autodiscover.xyzcompany.com/Autodiscover/Autodiscover.xml), which can be found in the worker log as it attempts to login by searching for "Discovered endpoint:" or "AutoDiscover".