Maximum credits exceeded

Hi,

Our website owner received an email:

You getting this message because an error detected while delivered your email.
For the domain: https://food2nourish.com.au
The log to paste when you open a support issue:
Maximum credits exceeded

Also one client has received a WooCommerce email 10 times and another client an email 27 times.

Mailer: postsmtp
HostName: food2nourish.com.au
cURL Version: 7.62.0
OpenSSL Version: OpenSSL/1.0.2k
OS: Linux r233.syd1.hostingplatform.net.au 3.10.0-962.3.2.lve1.5.27.el7.x86_64 #1 SMP Sat Nov 30 02:18:52 EST 2019 x86_64
PHP: Linux 7.1.33 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=Yes, zlib_encode=Yes
WordPress: 5.3.2 en_US UTF-8
WordPress Theme: Bridge Child 1.1
WordPress Plugins: Admin Menu Editor, Akismet Anti-Spam, BackUpWordPress, Bridge Core, Classic Editor, Contact Form 7, Disable Gutenberg, Envato Market, Featured Images in RSS for Mailchimp & Other Email, WPBakery Page Builder, LiteSpeed Cache, Mailchimp for WooCommerce, MailChimp, Max Mega Menu, Post SMTP, Qode Instagram Widget, User Switching, What The File, Checkout Field Editor for WooCommerce, WooCommerce Customer/Order CSV Export, WooCommerce eWAY Payment Gateway, WooCommerce Subscriptions, WooCommerce, Wordfence Security, Yoast SEO, WP Crontrol, WP Mail Logging, WP Missed Schedule Posts, WP Recipe Maker, Smush, WP Triggers, Refer a Friend for WooCommerce PREMIUM
WordPress wp_mail Owner: /home/user/public_html/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email, PostsmtpMailer->get_mail_args, No3x\WPML\WPML_Plugin->log_email
WordPress wp_mail_from Filter(s): wordfence::fixWPMailFromAddress
WordPress phpmailer_init Action(s): wpcf7_phpmailer_init
Postman: 2.0.10
Postman Sender Domain (Envelope|Message): aimhigherweb.design | food2nourish.com.au
Postman Prevent Message Sender Override (Email|Name): Yes | Yes
Postman Active Transport: SendGrid API (https://api.sendgrid.com:443)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 8757 | 45
Postman Stealth Mode: Yes

What do we need to do here?

Thanks.
Steve