In Gmail when you have an email from a newslist, you get a 'unsubscribe' link next to the email address, like this:
Google+ <noreply-67e4f7ae@plus.google.com> Unsubscribe
There is header named List-Unsubscribe: which identifies the url or email.
In gmail I can see original of email to see headers:
Received-SPF: pass (google.com: domain of root@domain.net designates 123.123.123.123 as permitted sender) client-ip=123.123.123.123;
Authentication-Results: mx.google.com;
spf=pass (google.com: domain of root@domain.net designates 123.123.123.123 as permitted sender) smtp.mail=root@domain.net;
dkim=pass header.i=@domain.com
List-Unsubscribe: <http://domain.com/uns.html?test=wdqwqw>
I have List-Unsubscribe header set, spf and dkim verification pass.
What can be wrong? Why gmail does not show unsubscribe link?
The unsubscribe option is only shown for senders with a high reputation:
This only works for some senders right now. We're actively encouraging senders to support auto-unsubscribe — we think 100% should. We won't provide the unsubscribe option on messages from spammers: we can't trust that they'll actually unsubscribe you, and they might even send you more spam. So you'll only see the unsubscribe option for senders that we're pretty sure are not spammers and will actually honor your unsubscribe request. We're being pretty conservative about which senders to trust in the beginning; over time, we hope to offer the ability to unsubscribe from more email.
Also note that the preferred list-unsubscribe method is mailto, not http. Outlook.com for example only honors mailto.