Support » Plugin: Subscribe2 » Bug: Unsubscribe appears to be case sensitive on emails

  • Thanks for plugin.
    FYI A subscriber complained about not being able to unsubscribe. I tried entering her email via the front end subscribe/unsubscribe form. It said no such email.

    I then logged in the backend, and searched for the email address. It was there – the first letter was capitalised. So the search finds the email, but the unsubscribe does not because the ‘case’ does not match.

    • This topic was modified 1 year, 2 months ago by  anmari.
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  • @anmari

    This is expected behaviour and is consistent with internet emails standards. The latter part of an email address, the part after the @ is consider care insensitive but the part before the @ can be case sensitive.

    As such an email server can be configured to treat as a different email address than Subscribe2 needs to follow the published standards despite the fact that the majority of email servers treat the first part of the email as case insensitive as well.

    HI Mattyrob,
    while generally I agree with adhering to standards, it seems this is a case of ‘in theory’ vs ‘in practice’.

    the RFC 5321 spec (sect 2.4) says “the case sensitivity of mailbox local-parts impedes interoperability and is discouraged”

    There is a defacto standard (a widespread belief) that email addresses are case-INsensitive and many organistations and isps (gmail for eg) treat them as case insenstive. WordPress itself ignores case when checking if an email exists, ie it is not possible for AND to both register on a wp site.
    One could argue that the ‘public’ subscribe option should match this, and not allow multiple versions of the same email to be ‘subscribed’.

    Subscribing via a smartphone (well at least definitively with an iphone), prompts users to start the email address with a capital. Most would not even notice this. If they then try unsubscribe via a PC, it does not prompt them to start with a capital and they just get told that the email address does not exist. But then they still get the emails. Also I have seen a few clearly multi subscribes where they have subscribed more than once and not realised. This user issue causes stress for small clients (eg: a ballet studio), and I imagine others. Every year at beginning of year, kids have moved on and are no longer with the school, so there is a batch of unsubscribes, some of which ‘work’ and some of which do not. Can you imagine the frustration?

    A related issue is that they don’t see or click on the unsubscribe confirmation email and thus stay ‘subscribed’ despite thinking that they have unsubscribed – more angst! For their scenario, a quick unsubscribe (without confirmation) would be better. I realise this may not suit all, but again I do think is more in line with what people expect these days. When they want out, they want out now.

    So anyway I appreciate this is our problem. I’ll probably look at either an ‘unsubscribe’ addon plugin or maybe move them to something like mailchimp, which is bit more complicated than suits them.

    Some references showing belief and practice if the above was not convincing enough 😉


    Subscribe2 HTML adds the option to have unsubscribe links in the notification emails. Having stopped being the coder and supporter of this free version I’ve had the time to extend and add to the functionality of Subscribe2 HTML with much greater ease.

    As for the case sensitivity bit, your links kind of back up Subscribe2’s implementation. Despite RFC5321 discouraging case sensitivity on mail servers it says just before that, that the local-past MUST BE treated as case sensitive.

    Google avoid the issue by forcing the case to lower for all of their emails – problem avoided.
    M$ surprisingly follow the standard in this case and get hammered for actually following a standard for once!
    Sadly, it seems the Apple users fall foul of there experience where ‘everything just works’ on an Apple product and wrongly assume email addresses are case insensitive. Sadly, they’re still wrong.

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