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I manage an email newsletter for a customer. It uses a custom list management utility, but the emails are being delivered through SendGrid.

In order to integrate correctly with our list management unsubscribe. I'm manually creating the "List-Unsubscribe" header, with a mailto address, which goes to an email parser, and unsubscribes the user from the correct publication etc.

The email parsing etc. works fine. However for some reason gmail is not displaying the "Unsubscribe" link in the header, as it does with other newsletters I receive.

Another newsletter I manage for a different customer, uses SendGrid's built-in unsubscribe management, and for these ones gmail does display the link.

What I want to know, is why is my custom "Unsubscribe-Link" ignored by gmail, but SendGrid's works?

SendGrid's "List-Unsubscribe" looks like this ...

List-Unsubscribe: <mailto:unsubscribe@email.mycustomdomain.com?subject=http://links.mycustomdomain.com/asm/unsubscribe/*q*user_id=[SHA hash...==]>

My custom "List-Unsubscribe" looks like this ...

List-Unsubscribe: <mailto:u-[custom-encoded-user-id+publication-id]@list-management.mycustomdomain.com>

My email parser reads the incoming "to" address, and interprets the encoded user-id and publication-id, to unsubscribe the person from the correct list.

Can anyone suggest why gmail might not like my link? It's extremely difficult to find detailed information about the requirements for this header.

One obvious difference, is that mine doesn't have a subject, but that's because it doesn't need it. It gets all it needs from the "to" address. Could this actually make a difference though? Does the "to" address need to remain static?

I thought perhaps it just needed time, for gmail to familiarise itself with this newsletter. However it has been running for months, and still no link.

The list is very clean, and all recipients have opted-in. We don't get any spam reports, and very few bounces.

I've gone to a great deal of trouble to ensure that everything works correctly from my end, and it's very frustrating that I cannot find out what I need to do to make this work.

I found a similar question at the gmail forums, and the official response to that question was to "contact a professional about constructing html emails".

Not very helpful for me, as in my case, I'm supposed to be that professional.

Any suggestions would be greatly appreciated.

user1751825
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  • Might be low sender reputation? https://stackoverflow.com/a/28500968/1435647 – Vasiliy Zverev May 17 '18 at 13:39
  • Not sure, but you might double-check that the "local part" of the email address is no more than 64 characters long and that the entire email address is no more than 255 characters long. https://en.wikipedia.org/wiki/Email_address – rinogo Jun 18 '18 at 18:12
  • fwiw, even in iOS Mail, I've seen the header appear sometimes and not other times on our test emails. I'm guessing there's some sort of additional underlying logic influencing whether or not the "unsubscribe" UI is displayed. – rinogo Jun 18 '18 at 18:13
  • Is the issue fixed? – Aarthi Oct 31 '18 at 05:56
  • I reverted back to using SendGrid to temporarily get around the issue. I may try the custom list management again in the next couple of months. – user1751825 Oct 31 '18 at 07:06
  • I also experience this. My List-Unsubscribe header is very non-custom: `List-Unsubscribe: , ` - but the "Unsubscribe" link does not appear in GMail. It is very puzzling.The header is recognised and appoved by https://mail-tester.com. I think that the comment from @VasiliyZverev links to the correct answer, and that this is duplicate. – Free Radical Oct 28 '20 at 07:42
  • Does this answer your question? [Gmail unsubscribe link does not appear](https://stackoverflow.com/questions/28497332/gmail-unsubscribe-link-does-not-appear) – Free Radical Oct 28 '20 at 07:49

1 Answers1

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Apparently, Google uses some additional heuristics to decide whether the link should be displayed or not. The List-Unsubscribe header could be abused by spammers to validate that their target got the message, and thus, GMail only shows the unsubscribe link if the source of the message has accumulated sufficient trust.

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See https://support.google.com/mail/thread/49653586?hl=en&msgid=49801705 for a response posted on Google Support.

Pierre Arnaud
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