#2256 ✓resolved

Root Certificate - says expired and is not

Reported by FlyboyArt | February 12th, 2019 @ 03:45 AM

I used the ProtonMail bridge application to connect to the ProtonMail server. The Bridge has been working fine for a year and now I get a message each time I start MailMate claiming the root certificate is "not trusted". However this is not true, the certificate was renewed on 06-Feb-2019 and is good for a year. (see attached image file).

Can you find out why MailMate is reporting the certificate is"not trusted"?

Thanks, Art

Comments and changes to this ticket

  • benny

    benny February 12th, 2019 @ 10:09 AM

    • State changed from “new” to “resolved”

    In short, you have to explicitly trust the certificate.

    Note that MailMate is not claiming the certificate expired. It is telling you that it cannot verify the certificate received from I first thought this would make sense if the common name used in the certificate was some IMAP hostname, but it isn't. It's actually But MailMate is also not claiming a mismatch in the hostname.

    It appears the certificate is quite new (not valid until after February 6th 2019), so my guess is that something has recently changed with the bridge certificate or the same thing happened a year ago and you told macOS to trust the certificate.

    It makes sense that the system (macOS) is not, by default, setup to trust a ProtonMail root certificate on since ProtonMail does not “own” that IP address. I'm not an expert on these issues and I'm not sure what would be a better solution. My guess is that it would be better if ProtonMail used a real server address as the Common Name of the certificate and then used a properly verified certificate. This would allow me to introduce a setting which would make MailMate compare the certificate with the “real” server name instead of It would be a somewhat confusing setting, but it could, e.g., just appear when using or localhost in the IMAP/SMTP settings.

    Do let me know if you find anything indicating that MailMate is doing something wrong.

    (I assume, by the way, that you would get a similar error from other desktop email clients.)

  • benny

    benny February 12th, 2019 @ 10:43 AM

    You can use “Mailbox ▸ New IMAP Mailbox” to create a mailbox in the account and then use “Mailbox ▸ Take Offline” to take it offline. Finally, if needed, use “Mailbox ▸ Mailbox Type” to make sure it is used for drafts.

    A Drafts folder cannot work with ProtonMail because it would mean that non-encrypted (unfinished) emails could be uploaded to the server.

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Mac OS X email client.

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