FAQ

General

Why are the links in my email not clickable?

That is Link Guard working. Every web link stays inactive until you approve its destination host. Click the notice at the top of the message, check the hosts, and choose Allow temporarily or Allow permanently. See Getting started.

Does Link Guard send my mail anywhere?

No. Messages are checked inside Thunderbird and nothing about them is sent anywhere. The only network requests are fetches of list sources you add yourself. See Privacy.

Does it come with a list of trusted sites?

No. Link Guard ships no trust list – you decide what to trust. To start quickly, approve the domains you use often as whole domains, or import an allowlist that your organisation provides.

Is this a virus scanner?

No. Link Guard shows you where links go and asks you to decide. It does not scan websites or attachments. See Security model.

How do I update Link Guard?

Install the newer XPI from the releases page the same way as the first one. Your settings are kept. Link Guard does not update itself.

Which languages are supported?

Chinese (Simplified and Traditional), Czech, Danish, Dutch, English, Finnish, French, German, Hungarian, Italian, Japanese, Korean, Polish, Portuguese (Brazil), Russian, Spanish, Swedish, Turkish and Ukrainian. Link Guard follows Thunderbird's interface language and falls back to English for others.

Approving and blocking

What is the difference between "Allow temporarily" and "Allow permanently"?

A temporary approval applies to the message on screen and ends when you show another message. A permanent approval is remembered and appears in Settings.

Should I approve the exact host or the whole domain?

Approve the exact host when you trust only that service, for example login.example.org. Approve the whole domain (example.org and all subdomains) only for organisations you trust completely, ideally domains you control. See Approvals and blocks.

Why can't I approve docs.google.com (or a github.io site) as a whole domain?

Anyone can publish documents or pages on these hosts. A whole-domain approval would also approve content written by strangers, so Link Guard only offers an exact approval. See Shared-content hosts.

Why can short links like bit.ly only be allowed for one message?

A short link hides its destination; approving the shortener permanently would approve every destination anyone links to through it. If you do not want this protection, switch off the Public URL shortener warning in Settings.

Why can't I approve a link to an IP address permanently?

IP addresses change owners and say nothing about who runs a server. Links like https://192.0.2.10/ can be allowed for the current message only.

I approved the whole domain, but a link on it is still inactive. Why?

Either the link has a warning – links with warnings need an approval of their exact host – or the host is a shared-content host, or a block covers it. The notice shows which applies. See Troubleshooting.

How do I undo a decision?

Open Settings, remove the line from the relevant card and click Save changes. A block can also be undone right in the message: click Unblock and confirm.

Warnings

Why does Link Guard warn about a link I know is fine?

Warnings are heuristics. A lookalike warning can hit two legitimate, similar names; an internationalized domain can be genuine; link text can name a domain while the link goes through a tracking service. Approve the exact host if you are sure. If a type of warning is consistently unhelpful for you, switch it off in Settings.

The warning stays after I approved the host. Is that a bug?

No. Warnings stay visible next to the link on purpose, so that the reason for caution is never hidden once a link works.

Why do Outlook "safelinks" links say Possible redirect to …?

Microsoft Safe Links and similar services wrap every link in your organisation's mail. The visible host is the wrapper, not the site you will reach. Link Guard reads the real destination from the wrapped link and names it, so you can judge it. Once that destination is approved, the warning disappears. See Warnings.

Why can a link to my bank only be allowed for this message?

Its address contains script or HTML code. That is how cross-site scripting attacks a site you trust, so a lasting approval of the host is deliberately not enough. See Warnings.

Why don't I get lookalike warnings?

The lookalike check compares links with domains you have approved. With no approvals yet, there is nothing to compare against. See Warnings.

Layout

The labels next to links break the layout of some newsletters. Can I turn them off?

Yes. Switch off Show link destinations in Settings. This hides the grey ↗ host labels next to ordinary links. Red warning labels and the notice remain.

Can a message hide the notice?

A message cannot hide, restyle or fade the notice or the labels with its own styles. It can draw something on top of them. The Link Guard toolbar button is outside the message and always shows the real count. See Security model.

Lists and rules

Where do I get lists?

Link Guard does not recommend list providers. You can write your own (the format is simple JSON) or use a list maintained by your organisation.

My remote list does not load. What is wrong?

The source must use HTTPS, allow CORS, answer without a redirect, use the content type application/json or text/plain, and stay under 512 KiB (64 KiB for a warning list). See Troubleshooting.

Can a list approve links I have not reviewed?

A list does nothing until you have reviewed it in the preview, enabled it and saved. Allowlists never update themselves. Blocklists can update themselves, but an update can only block, never approve.

Can I use any regular expression in warning rules?

Most everyday features are supported: classes, groups, alternatives, anchors and quantifiers. Backreferences, lookaround and \b are not, because they would allow patterns that freeze the program. See Warning rules.