No emails getting through

Hi, we have spent a lot of time trying to resolve this issue. We are suddenly not receiving emails. I have included the diagnostic information below generated by Postman SMTP. We are using Contact 7 plugin. We have reinstalled this in case the plugin had become corrupted. We have made no other configuration changes to the site The host provider says they have made no changes either that could have caused this. Any help in getting our contact forms working again would be greatly appreciated. Thank you in advance, Ben

OS: Linux cpanel2.hostireland.com 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64
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: 4.6 en_GB UTF-8
WordPress Theme: BIG CITY
WordPress Plugins: Akismet, bbPress Enable TinyMCE Visual Tab, bbPress, Cimy User Extra Fields, CLEditor for WordPress, Comet Cache, Contact Form 7 Honeypot, Contact Form 7, Easy Theme and Plugin Upgrades, Ecwid Shopping Cart, Favicon XT-Manager, List category posts, Postman SMTP, Recently Registered, BJD Responsive iFrame, Sidebar Login, Tabby Responsive Tabs, Tismy User Profile Upload, Wordfence Security, WordPress Page Widgets, WP Twitter Feeds, WP Widgets Shortcode
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
WordPress phpmailer_init Action(s): wpcf7_phpmailer_init
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: SMTP (smtp:tls:oauth2://smtp.gmail.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 341 | 84