There has been a lot of fuzz around the change to Gmail about 1 week ago which literally broke millions of SMTP servers used with Gmail around the world. It seems that Gmail started check also Reverse DNS for the IP address of the SMTP server and require that the Reverse DNS host has valid SSL certificate, too. Earlier it was enough that just the SMTP host had a valid SSL certificate. This combined with horribly misconfigured shared hosting servers caused the global meltdown of shared hosting SMTP servers.
How it does not work now

Here is how it works with the domain name of this forum, webseodesigners.com.
The domain name has a valid SSL certificate.
The domain name points to IP address 166.62.7.52. The Reverse DNS hostname of the IP address is ip-166-62-7-52.ip.secureserver.net.
ip-166-62-7-52.ip.secureserver.net does not have a valid SSL certificate. That is why Gmail is throwing the following error and refusing to use the SMTP server:

Poople Gmail wrote:TLS Negotiation failed, the certificate doesn't match the host., code: 0

How it should have always worked

Naturally GoDaddy should have a valid SSL certificate also for the host in their Reverse DNS, or use the same host name they are using with the cPanel that already has a Reverse DNS with valid SSL cerficate:
Tools

• For checking Reverse DNS: https://mxtoolbox.com/ReverseLookup.aspx
• For checking SSL certificates: https://www.sslshopper.com/ssl-checker.html
• Solution for GoDaddy shared hosting users

Obituary for Gmail

It seems that many hosting companies got surprised and reacted to this like they react to everything: blaming third parties, blaming each other, blaming google and dodging responsibility. Also Poople did very badly doing such a big change with huge impact without informing hosting providers and Gmail users beforehand and giving them time to fix their broken systems.

I hope to find or make something to replace Gmail. For my search needs I am using DuckDuckGo and I wrote my own photo album management system to replace Poople Photos/Picasa.