Introduction

ESPs (Email Service Providers) can be excellent sources for segmented user traffic.

One of the problems with ESPs is recording clicks while keeping deep linking functionality intact. ESPs wrap deep linking URLs with their own ESP's click recording domain. This procedure sometimes breaks the iOS Universal Links process.

With Sailthru, which supports Universal Links on top of their click recording domain, deep linking and click recording can still be performed.

Prerequisites

Setting up Sailthru

Step 1: Setting up link branding in Sailthru

Create a dedicated click recording domain and set a subdomain (for example, click.example.com). This can be done by purchasing a designated domain or using your own domain.

For more information on setting a click recording domain with Sailthru, see here.

Step 2: Upload AASA file to Sailthru

For Sailthru to support iOS Universal Links, an AASA file is required.

When you set up OneLink with Universal Links, you already have an AASA associated with the OneLink. To obtain the AASA:

1. Go to OneLink templates and find a OneLink that is configured with Universal Links.
2. Add /.well-known/apple-app-site-association to the end of the OneLink URL.
3. Paste the OneLink in the browser address bar and hit enter. For example, <OneLinkSubdomain>.onelink.me/.well-known/apple-app-site-association. When you do so, the AASA file is downloaded to your computer. You can open it using any simple text editor.
4. Upload this AASA file to Sailthru. For more information and to learn more about the contents of this file, see Sailthru's guide.

Setting up your app to support Universal Links

Step 1: Associating click domains in Xcode

1. In Xcode, click on your project.
2. Click on Capabilities.
3. Turn Associated Domains on.
4. Click the + sign and add your click domain. For example, applinks:click.example.com.

Step 2: Resolving deep links

The SDK needs to resolve the OneLink behind the click domain to get the campaign details. The details are returned in the onAppOpenAttribution method.

To resolve click domains:

1. Make sure that your SDK version is at least 4.9.0.
2. List the click domains in the SDK property resolveDeepLinkURLs. This property needs to be set before SDK initialization. For more information, see SDK documentation here.
   
   Objective-C Swift

   [AppsFlyerTracker sharedTracker].resolveDeepLinkURLs = @[@"example.com",@"click.example.com"];

   AppsFlyerTracker.shared().resolveDeepLinkURLs = ["example.com", "click.example.com"]
   	

3. Add the following code so that the SDK can resolve the click recording domain:
   
   Objective-C Swift

   Add this code in AppDelgate.m

   - (NSDictionary *)allHTTPHeaderFieldsForResolveDeepLinkURL:(NSURL *)URL {
   		if ([URL.host isEqual: @"click.example.com"]) {
   			return [NSDictionary dictionary];
   		}
   		else {
   			return nil;
   		}
   	}

   Add this code in AppDelgate.swift

   func allHTTPHeaderFields(forResolveDeepLinkURL URL: URL!) -> [String : String]! {
   		if (URL.host == "click.example.com") {
   			/// Change User-Agent
   			return [:]
   		} else {
   			return nil;
   		}
   	}
   	

Sending your first email

1. Create a OneLink URL on the Link Management page (or manually). 
2. When creating the OneLink URL, make sure to URL-encode all parameter values.
3. The following parameters are highly recommended to use:
   • pid (media source) - Use a media source that signifies this usage such as Email.
   • c (campaign) - The name of the campaign you want to measure.
   • af_dp - The deep link URI scheme you want to deep link your users into.
   • af_web_dp - Where to redirect users clicking the link on desktop.
   • af_ios_url - Where to redirect users that don’t have the app clicking the link on an iOS device.
   • af_android_url - Where to redirect users that don’t have the app click the link on an Android device.
4. Place the OneLink URL in the email that you create in Sailthru. Example:

   <a href="greatapp.onelink.me/abcd/1234567">Download my great app!</a>

   At this stage, Sailthru wraps the above link with the click domain that you set in the previous steps. Any click on the click domain redirects to the OneLink attribution link. If the app is installed on the user's device, the click domain deep-links into the app.

https://greatapp.onelink.me/abcd?pid=Email&c=Spring_Newsletter&is_retargeting=true&
	af_dp=testapp://path/to/content&af_web_dp=https://www.example.com/path/to/content&
	af_ios_url=https://www.example.com/path/to/content&af_android_url=https://www.example.com/path/to/content

Testing your links

After following all the required steps mentioned above, creating the appropriate OneLink URL, and placing it in an email, send yourself a test email.

What should you expect?

If you have the app installed, the app should be invoked. If the relevant AppsFlyer SDK deep linking APIs are implemented you should be deep linked into the relevant content.

In addition, a click should appear in both the AppsFlyer dashboard, attributed to the provided media source and campaign, and also in Sailthru data.