"wp_mail declared by another plugin or theme"

I’ve disabled all plugins and run the diagnostic test (below), but still getting the wp-mail conflict notice. I had previously had Wp-Mail-SMTP installed (now uninstalled). Is it possible it makes changes to the WP installation that aren’t reverted when the plugin is disabled/deleted?

PHP: Linux 5.4.45 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=Yes, zlib_encode=Yes
WordPress: 4.4.1 en_US UTF-8
WordPress Theme: SailMV Theme
WordPress Plugins: BackWPup, Conditional Widgets, Contact Form DB, Contact Form 7, Ditty News Ticker, Find and replace, Flamingo, Genesis Responsive Slider, Genesis Simple Edits, Genesis Title Toggle, Simple Calendar, jonradio Multiple Themes, Menu Items Visibility Control, Menu Social Icons, Meta Slider, Postman SMTP, Really Simple CAPTCHA, Regenerate Thumbnails, Show Hide Author, wp-jquery-lightbox, WP Super Cache
WordPress wp_mail Owner: /home/sailmv/public_html/wp-includes/pluggable.php
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
Postman: 1.7.2
Postman Sender Domain (Envelope|Message): sailmv.org | sailmv.org
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: Gmail API (https:oauth2://www.googleapis.com:443)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 0 | 0

https://wordpress.org/plugins/postman-smtp/