Android Outlook App - Email server certificate is invalid

I went to the link.  That sure is complex for what should be an easy thing to fix.

Hi CJPrescott what did you choose as an alternative as I am losing the will to live with this elongated fix.

Do you seriously expect users to go through this long certificate process just to use the Outlook app on Android? 

What a joke! No other email client has this issue (which by the way was not an issue earlier). 

Pleade get a reality check and solve it properly in the app itself. 

The solution works (least for me) but makes it seem far more complicated than it actually is. It's also based around have internet explorer on windows. it indicated 4 certificates, but for me at least, there were only 3.

I use chrome on linux, so don't have the windows certificate manager the solution talks about - nor did I need it - but I would think chrome on windows will work in the same way.

using chrome:

I simply logged into office.com, and once logged in and at the home page, clicked on the certificate lock icon to the left of the URL. Click certificate > Details,

then click the top certificate in the chain, then click export, save as x509 type

then click the next certificate down in the chain, click export, save as x509 type

then click the 3rd and last certificate in the chain, export, save as x509 type.

copy the 3 files to my android (10) phone, and imported them:

Settings > Security > Encryption & Credentials > Install from SD Card, browse to where I copied the .cer files and followed the prompts.  (Despite being called SD Card, After tapping, I found it allows you to browse to internal storage, cloud storage etc, wherever you saved the .cer files.)  

after that, I was able to outlook. 

but, yeah, shouldn't have to do this, I expect more from Microsoft.

I was getting the same error after upgrading my Outlook Mobile App for Android. I fought with this for a day and half, spent hours on hold with technical support from both Microsoft and my email provider. It appears I solved the problem for me at least. 

I removed my email acccount and set it back up from the beginning using advanced settings. I have my account setup as an IMAP account. I got the certificate error but told it to login anyway. I then got an smtp error. I went back to my settings and added port information at the end of my smtp settings.

My smtp setting now reads: smtp.mydomain.com:587

The Outlook for Android let me set up the account and hasn’t given me an invalid certificate error message as of yet. Hopefully this solves a problem for some of you.