Your mail server certificate is invalid error

thanks

I've got the same issue on mine as well. Updated to the latest app version 2.2.143 for android and the invalid certificate error has only just happened a couple of days ago. Tried uninstalling, re-installing, restarting even factory reset and nothing has worked. If Microsoft have updated the android and apple apps to only take TLS1.2 then its possible the the ISP's may not have updated yet or the app itself is still using the older 1.0/1.1 but this seems unlikely as I've also checked using the stock gmail app and it is working and accepting the imap.tiscali.co.uk address fine however they may also be using the older TLS1.0/1.1. I've also tried another app that kind of looks like outlook but isn't and its also working fine so what ever the problem is, It could be with the ISP's still using the older TLS certificates

This would be down to ISps to do this, not indivual users. Talktalk is not my ISP, but my email is Tiscali, which I have and have had when I was with Tiscali ISP, but they were taken over by tallktalk.

I had a chat with Microsoft regarding this yesterday.  They have dropped support for TLS1.0 and 1.1 and are requiring TLS 1.2 if you want to use the app.  I am currently in process of bringing up a new 2008 R2 server to move my web facing traffic to, you can have multiple CAS servers so you do not have to remove/delete/decommission your existing, just add a new web facing server to take the role of internet facing owa/activesync/outlook anywhere (if you have it).

Have been messaging talktalk via Twitter, not got very far so far, was asked whether I can log-in to my mail via webmail, will keep people updated of any further development if I get any, as Microsoft say providers need to update to TSL 1.2, let us see if they do. I have tweeted them the link to this thread, by the way.