Error authenticating with this Client ID

Hi,

I am creating a website using wordpress in GAE. I using postman plugin to send mail from my site but it showing error.
“Error authenticating with this Client ID”

I give type as SMTP.
Outgoing Mail Server Hostname :smtp.gmail.com
Outgoing Mail Server Port :587
Security: STARTTLS
Authentication :oAuth 2.0.
i give all the client details correctly.
After configured the OAuth 2.0 authentication. i click grant permission. then click allow.
After that a error show

Error authenticating with this Client ID. [Error executing wp_remote_post: 0: php_network_getaddresses: gethostbyname failed. errno=0]

while i check the log detail. It show status as “Could not open socket”

how to solve this problem help me.

Diagnostic Info

PHP: Linux 5.5.26 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=Yes, zlib_encode=Yes
WordPress: 4.3.1 en_US UTF-8
WordPress Theme: Enigma
WordPress Plugins: Beauty Contact Popup Form, Contact Form DB, Contact Form 7, Easy Google Fonts, Easy Social Icons, Favicon XT-Manager, Lightweight Social Icons, MaxButtons, Page scroll to id, Popup contact form, Postman SMTP, Simple Social Icons
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
Postman: 1.7.2
Postman Sender Domain (Envelope|Message): gmail.com | gmail.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: Default (smtp:none:none://localhost:25)
Postman Active Transport Status (Ready|Connected): No | No
Postman Selected Transport: SMTP (smtp:tls:oauth2://smtp.gmail.com:587)
Postman Selected Transport Status (Ready|Connected): No | No
Postman Deliveries (Success|Fail): 33 | 15
Postman File Locking (Enabled|Temp Dir): No | /tmp

https://ww.wp.xz.cn/plugins/postman-smtp/