We can implement customized list-ID if you request it : it's easy for us to put it in place for you. But we don't recommend it because adding non-standard header, makes the message non-standard and there are risks that the validation / anti-spam filter detects it as bad.
« List-ID » is an unpleasant case:
• It's a spec based on an RFC published more than 10 years ago!
• Nobody has really implemented it
• Those who implemented it did it the wrong way
According to the spec, it should look like that :
List-ID: "YOUR WEB SITE Daily Deals" <daily-deals.list-id.yourwebsite.ru>
The part before <> is a text description (unused) and between <> we have a DNS name that should absolutely be a domain controlled by the sender.
It's a simple idea. But this "standard" doesn't include ANY protection to protect the identity of the list (there's no DNS record to validate this identity). Therefore anybody could copy your list-ID structure or copy any other list-ID of anybody else and recipients will never make the difference.
Because of this lack of security, nobody has really used List-ID around the world or implemented anything around this concept. And the fact that Gmail shows it or that Yandex recommends to use it, doesn't change that it's not a popular or a best practice.
But once again, knowing the risk we mentioned (non standard headers + security), if you still want to implement customized list-ID for your headers, we can implement it easily for you.