Email mail settings gives error in nextcloud

🍱 Features & apps 💌 Mail
1

Mail Setting does not work and gives this error:

A problem occurred while sending the email. Please revise your settings. (Error: Connection could not be established with host smtp.gmail.com :stream_socket_client(): php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution)

I am certain the settings I entered in Nextcloud > Settings > Basic Settings > Email Server
are correct.

from ther server command line I can ping

$ ping  smtp.gmail.com 
PING smtp.gmail.com (66.102.1.109) 56(84) bytes of data.
64 bytes from wb-in-f109.1e100.net (66.102.1.109): icmp_seq=1 ttl=105 time=13.3 ms
64 bytes from wb-in-f109.1e100.net (66.102.1.109): icmp_seq=2 ttl=105 time=14.0 ms

my gmail smtp settings are enabled.

2

You can try to debug with swaks. (Swiss Army Knife for SMTP).

3

Login into your GMail account. There you might find in one of the submenus a message, that there was an attempt to login with an unsave mail-client.
Google determines, what save and unsave clients are. You may allow permission through Nextcloud, but it only will work for a couple of weeks. Then it becomes blocked again.