iPhone error "Cannot verify server identity 'outlook.office365.com'" behind ATP100

ChipConnJohn

Hello All,

I started getting a pop-up on my iPhone today.

Cannot Verify Server Identity
The identity of "outlook.office365.com" cannot be verified.

When I click Details on the error I see:
dnsft.cloud.zyxel.com
issued by Amazon RSA 2048 M01

I can't find any app that isn't actually updating.  I think it's the iOS Mail App that's causing the pop-up as when I'm behind the ATP100 I see an Account Error at the bottom.  This goes away if I use cellular.  Either way the email is getting updated, however.

Any ideas why the ATP100 is getting in the way of verifying this certificate?

Thanks,
-John

Zyxel_Kevin

Hi @ChipConnJohn,
Greeting Forum, there is flase positive by content filter. 
The site has been categorized into the correct category.
If the issue still we can have remote session to check issue. Thank you
Kevin

Chris71

Hi all,

same here: MS Outlook 365 23.01 behind ATP100W....

Since a few days, and everytime we start Outlook, there are one or more of this security alerts, with different MS-domains....

Thanks! Chris

Freddy

Same here as Chris71 (behind ATP500) with the following signatures:

Chris71

Hmm, probably this helps... we'll give it a try:

https://support.zyxel.eu/hc/en-us/articles/10081056405650

ChipConnJohn

Perfect! Seems resolved and article makes sense. 

Zyxel_Kevin

Hi @Freddy, 
Greeting Forum.
Actually the accidient had resolvd on 2/14 10am GMT+1. 
Please try to clear your DNS cache and check if the issue still persist. 
Thank you
Kevin