Yahoo Mail iOS fails to launch Apple eSIM provisioning links after Plunk click tracking redirect

[denzilc]

Yahoo Mail iOS fails to launch Apple eSIM provisioning links after Plunk redirect

Description

A direct Apple eSIM provisioning link works in the Yahoo Mail iOS app. However, the same link fails when Plunk click tracking wraps it in a tracking redirect.

The tracked link works in Spark and Apple Mail.

To Reproduce

1. Send an email containing an Apple eSIM provisioning URL.
2. Allow Plunk click tracking to rewrite the link.
3. Open the email in Yahoo Mail on iOS.
4. Tap the tracked link.
5. Compare with:
   • The direct Apple URL in Yahoo Mail.
   • The tracked URL in Spark or Apple Mail.

The tracked URL has this structure:

https://track.useplunk.dev/CL0/https:%2F%2Fesimsetup.apple.com%2Fesim_qrcode_provisioning%3Fcarddata=.../...

The Plunk endpoint returns:

HTTP/2 302
Location: https://esimsetup.apple.com/esim_qrcode_provisioning?carddata=...

Expected behavior

The tracked link should redirect to Apple’s eSIM provisioning flow and start installation in Yahoo Mail iOS.

Environment

Please select the option that applies:

• Deployment type:

• Hosted

• Self-hosted

If self-hosted, please provide relevant details (Docker, Kubernetes, bare metal, etc.):

Not applicable.

Version verification

⚠️ Important:
Self-hosted issues must be reproduced on the latest commit.
Issues without a confirmed commit SHA may be closed without investigation.

• I am using the hosted version

If self-hosted:

• I have confirmed this issue still exists on the latest commit (not the latest tag)

• Commit SHA tested: N/A

Logs / Error output

If applicable, add logs, stack traces, or error messages here.

No browser error is shown. The tracked link simply does not launch the Apple eSIM installation flow in Yahoo Mail iOS.

Screenshots / Recordings / Additional context

• The direct Apple URL works in Yahoo Mail iOS.
• The identical Plunk-tracked URL works in Spark and Apple Mail.
• The copied URLs from Yahoo Mail and Spark / Apple Mail are identical.
• The Plunk redirect resolves to the expected Apple URL.
• The issue appears specific to the interaction between Plunk click tracking and Yahoo Mail iOS.

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Checklist

Please confirm the following before submitting:

• I have searched existing issues to ensure this bug has not already been reported
• I have provided clear reproduction steps
• I have included all relevant environment details

[driaug]

Seeing as this issue only happens in one specific client, it is more suited for that email client than for Plunk.
I am unsure if this is something that can be resolved on Plunk's end

[denzilc]

Yeah sure, I will register a bug with Yahoo Mail iOS app. That said, I have only discovered this bug in Yahoo Mail. It may exist in more email clients. The other way to look at this is to investigate and check why it happens. The report might sound Yahoo Mail specific but may occur outside too.