Here is sample script (alias.sh) to add group members to alias:

koodivaramu.eesti.ee/rahvusarhiiv/sm

To get started, monitor what you are doing in web interface:

1) open browser developer tools (F12)

2) add new alias

3) open "Network" section and select "alias-put"

 - from "Headers" you can see what the API url is: /api/v1/settings/domain/alias-put/

 - from "Payload->view source" you can see what is sent to API

You can check out this thread as well. 

# Define path segments as arrays
slash = "/"
auth_parts = ["api", "v1", "auth", "authenticate-user"]
auth_uri = hostname + slash + slash.join(auth_parts)

list_search_parts = ["api", "v1", "settings", "domain", "account-list-search"]
list_search_endpoint = slash.join(list_search_parts)

delete_parts = ["api", "v1", "settings", "domain", "alias-delete", alias_name]
delete_endpoint = slash.join(delete_parts)

update_parts = ["api", "v1", "settings", "domain", "alias-put"]
update_endpoint = slash.join(update_parts)

Ok, so you are able to create the alias via the API but are not able to use it. 

1. yes i can send from gui in domain gui TO that email just has one option "Send email" 

2. no but this is supposed to be for a incoming email forwarding to another email

3. yes            

pastebin dot com slash 7g66mrzA if you want to check out the python script