Feature · Secure device linking
Secure Device Linking: Open the Same Temporary Inbox on Your Phone
Link a MailOnce temporary inbox from your computer to your phone with a rotating QR request and browser approval, without sharing the inbox publicly.
8 min read
MailOnce
Secure device request
Current inbox
New device
Quick answer
MailOnce lets you scan a rotating QR code from another device, then asks the browser that already controls the inbox to approve or refuse the request. Scanning alone does not grant access.
In this feature guide
Why link a temporary inbox to another device?
A verification message may arrive on your computer while the app or website asking for the code is on your phone. Recreating the inbox, forwarding a message, or manually moving codes between devices adds friction to a task that should be quick.
Device linking keeps the same active MailOnce inbox available where you need it. The goal is continuity between your own devices, not a public share link.
How MailOnce device linking works
The browser that already has the inbox displays a rotating QR code. A second device scans it and sends an access request. The original browser then shows the request and lets you accept or refuse it.
Only after approval should the second device open the same inbox and receive its live updates.
Open the QR link option in your active inbox
Scan the rotating code with the second device
Review the request in the browser that controls the inbox
Accept or refuse the request
After approval, open the same inbox on the second device
Why scanning the QR code is not enough
A QR code can be seen or scanned by the wrong person, especially on a shared screen. Treating the scan itself as authorization would make proximity enough to request and obtain inbox access.
MailOnce separates discovery from permission: the QR starts the request; the browser that controls the inbox decides whether it is allowed.
The key rule
Scan to request. Approve to enter. A QR scan by itself should never be treated as permission.
What the approval step protects
The approval prompt gives the current user a deliberate checkpoint before another device joins the inbox. An unexpected request can be refused instead of silently becoming a new session.
This is especially important for a temporary inbox because verification codes and sign-in links can be time-sensitive and should not be exposed merely because someone captured a QR code.
Same inbox
Continue with the inbox that is already receiving your messages.
Browser approval
The existing session stays in control of the access decision.
Rotating request
The QR is designed for a short linking flow rather than a permanent public URL.
Real-time continuity
Approved devices can follow the same active inbox instead of creating another one.
Useful situations for cross-device access
Cross-device access is useful when a signup starts on desktop but the code is needed on mobile, when a download or test flow moves between devices, or when you simply want to watch the same temporary inbox without rebuilding it.
It is a convenience feature for one active inbox, not a replacement for a permanent synchronized mailbox.
Privacy and shared-device precautions
Approve only a device you recognize. On a borrowed or public phone, leaving the inbox open can defeat the privacy benefit of the approval step.
Temporary email also does not make the rest of your activity anonymous. The websites you use can still collect the information and technical signals you provide to them.
If you did not initiate it
Refuse an unexpected device-link request. Do not approve it simply because the prompt appeared.
Device linking vs forwarding or sending yourself a code
Forwarding creates another copy or route for a message. Sending yourself a code exposes that code to another mailbox. Device linking instead keeps you inside the same MailOnce inbox after an explicit access decision.
For short-lived verification tasks, that can mean fewer copies and less manual handling while preserving the temporary nature of the inbox.
The practical takeaway
Use device linking when the same short-lived inbox needs to follow you from one device to another. The security boundary is the approval step: scanning requests access; it does not authorize access.
Try MailOnce
Keep one temporary inbox across your devices
Create your temporary inbox, then link another device when your verification flow moves from desktop to phone.
Create temporary email