List-unsubscribe link is not always appearing in ISP's
HI Community!
We have been working on a list-unsubscribe hybrid solution supporting both one-click as well as mailto: options.
While testing this however, I am experiencing that the unsubscribe link is not consistently appearing in the emails, but only sometimes.
I am really puzzled about why this is and also a bit concerned with implementing the headers, since I am not 100% confident with my test results since it does not always work.
This behaviour is observed in both apple mail app, as well as gmail app + web.
I can confirm that both the mailto: as well as the http post request are indeed working, just not always showing.
Any clue why this may be the case?
Thanks a bunch!