Hi, this is the same issue as as described here for Mozilla Thunderbird: [[No support of 64bit PKCS#11 drivers for signing device (i.e. smart cards) on 64bit Thunderbird|64bit Thunderbird issues with 64bit PKCS#11 drivers]] – Firefox 122.0 (64-bit) – Windows 11 Pro 64bit (– Thunderbird 64bit) Even though, I use a 64bit version of Firefox, it is not able to load any 64bit PKCS#11 module for security devices. Tried on several different PCs and several different 64bit PKCS#11 drivers for different smart cards. When I try to load e.g. C:\Windows\SysWOW64\eop2v1czep11.dll for the [https://info.identitaobcana.cz/eOP/OvladaceKarty.aspx Czech eID], it returns "Unable to add module". When I do the same from C:\Windows\System32\eop2v1czep11.dll, it works. The issue is that some issuers of qualified and commercial certificates (like e.g. [https://www.kb.cz/en/certification-services-kb Komerční banka]) do not issue a 32bit version of PKCS#11 drivers for their smart cards anymore and the only driver available is C:\Windows\SysWOW64\mopkcs11.dll, which cannot be loaded by Firefox or Thunderbird either. I don't see a problem in implementing the support for 64bit PKCS drivers in a 64bit browser and a 64bit email client. And if it does have the support, then there is something wrong going on.