I figured it out: it was a new gmail account and needed to confirm (again) my identity, this time through SMS.
Tks!
OS: Linux atl4vux158 3.2.51-hardened-r2 #1 SMP Wed Apr 9 01:43:29 UTC 2014 x86_64
HTTP User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36
PHP: Linux 5.6.9-pl0-gentoo C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=No, mcrypt=Yes
WordPress: 4.3.1 pt_BR
WordPress Theme: Unicon
WordPress Plugins: Akismet, Contact Form 7, Google Analytics by Yoast, Google XML Sitemaps, Jetpack by WordPress.com, WPBakery Visual Composer, Postman SMTP, Revolution Slider, Unicon Portfolio CPT, WordPress Importer, WP Super Cache
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
Postman: 1.6.24
Postman Sender Domain (Envelope|Message): gmail.com | gmail.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Transport URI: gmail_api:https:oauth2://www.googleapis.com:443
Postman Transport Status (Configured|Ready|Connected): Yes | Yes | Yes
Postman Deliveries (Success|Fail): 0 | 3