mail server invalid certificate?

[marbell]

For the last several days, my mother, who is also a TPG customer, has had a dialog when she starts up the Apple Mail application on an iMac OSX, saying that the certificate for mail.tpg.com.au is invalid - 'This certificate has an invalid issuer'. There is an option to tick a box next to 'Always trust "*.tpg.com.au" when connecting to "mail.tpg.com.au"' Should I tick that box?

A screen shot is attached. 

[sajalm]

Hi @marbell ,

Here is the link https://www.tpg.com.au/support/mac_mail.php for Mac email support.

Pls let me know if you still have issue,

Regards,

Sajal

[marbell]

The Apple Mail application settings are unchanged for over a year. This message has appeared in the last week. Do I need to be concerned about the contents of the message in the screenshot?

[david64 · Accepted solution]

Hi Marbell.

I have a similar problem which started last Friday evening (29/5). My device is an Android V4 tablet (quite old now) using the Chrome browser to access TPGs Post Office server. I got an error message indicating a certificate error.

The next morning I noticed that it had started working and it worked until midnight Saturday night. At that point, the certificate (the one on my tablet) that was being used by TPG web site expired. 

My resolution was to download the "COMODO RSA Certification Authority" certificate from Comodo and install it in the credential store on the tablet. 

That fixed the certificate error with Chrome and Post Office but it has affected the user interface a bit. I plan to upgrade Android V4 to V5 hoping that the newer certificate will come with it. This should also rectify the user interface.

I still think TPG changed something because the "AddTrust External CA Root" certificate you see in your picture expired on 30/5/2020 (on my tablet).

Out of interest, your mother might try using Safari browser to access www.tpg.com.au and see what happens.

You should contact Apple support re the Mail application on iMac OSX. Send the screen shot. You're wanting a fix for the certificate error. 

That may be a Mail application upgrade or OSX upgrade or just new certificates.

How old is the Mac OSX on the iMac?

(The setup provided by the moderator has SSL turned off which I think means that mail is sent and received in clear text. Not what you want.)