To make sure that your customer gets the Shipping confirmation letter with a tracking number in it, follow these instructions:
Firstly, you should go to Oberlo > Settings > Connected shops > Shop settings > General tab and add this link to custom tracking URL: http://www.17track.net/en/track?nums=.
Then make sure you have enabled this notification feature (http://take.ms/CCjs8) in Oberlo > Settings > Connected shops > Shop settings > General tab. Without it, your customer would only receive order confirmation notification.
Now, when you fulfill the Order through Oberlo (add tracking number from AliExpress), your customer will receive a notification about their order being shipped out.
However, Shopify has recently removed the tracking information from their default notification templates. Therefore, customers only received notifications about their orders being shipped, but without any tracking info. To fix this issue, you will have to edit your Shopify notification code: Go to Shopify > Settings > Notifications > http://take.ms/t66nY.
Then once you open it, you will have to remove all (http://take.ms/5HRAZ) code and replace it with the one that I attached to this letter. After that, just press "Save" on the top right corner of the screen and your customer will once again receive their order tracking information which will direct to 17track.net and show correct information!
Download the template code: http://s000.tinyupload.com/?file_id=06210876267996447687.