3.2 Proton Mail Bridge Users

About Proton Mail Bridge integration

thunderbird user.js enforces certificate strict PKP (Public Key Pinning) verification. This breaks software performing MITM (such as a local antivirus), or even Proton Mail Bridge.

When connecting Thunderbird for the first time to Proton Mail Bridge, this hardening measure (1223) must be relaxed :

• security.cert_pinning.enforcement_level to 1

Once incoming/outgoing servers enrollment is done, you may switch back to template value :

• security.cert_pinning.enforcement_level to 2