error code 85050025 - exchange email sync

As someone else noted, it appears to be an issue with the Exchange security certificate. 

Turning WiFi on/off didn't work for me.  I had to remote the account from the phone and re-add it.

Jim

I found that my phone was logging into BT fon and not into my home wifi, when I logged it into my home wifi the problem went away. Check that your phone is connected to your own wifi.

I was just about to post the same conclusion. I was having connectivity problems and noticed it was logged into a BT fon account, which is an OPEN connection (i.e. a public, unsecured network). Reverted to my home network (which is a secure connection) and it immediately synched up.

It looks like it lost the home network at some point and switched to the public network.  There must be (or should be ) a setting somewhere to define your default network.

In my case solution was a deletion of mail account and recreate. As a result - OS gave a message about old certificate (but all terms in certs is OK) and ask for continue.

I brought the Lumia535 dual sim phone 3 days ago, 1st day when i set up my work email, it works for less than 10 hrs.

Then, I got the synchronization error on 80072F89. Then, I uninstalled and install again on my 2nd day. It works for less than 5 mins, another synchronization error 85050025 appear. Then, I call the microsoft  window Phone hotline 21366338 in HK. The staff told me to do a factory reset. Then, I follow his instruction to do the factory reset. He said if after a factory reset still cannot work, then call them again. I tried but unsuccessful. I call again in the afternoon and talk to the CS staff call Mr. Jade Leung. He repeatedly ask me to follow his instruction same as before and try again but still doesn't work. He said he cannot help but ask me to contact the retailer to send to repair. I said how come a phone I just brought 3 days ago but I need to send to repair.  This is really ridiculous and disappointing as this is my first WP and I want to try see whether it is good or not. Obviously, I will never never never use WP again.

I will contact the retailer see whether they can change another phone for me or even I pay more to change to android phone again.

Really disappointing!