Post SMTP email error

Hi, I’m getting error emails saying ‘https://dreamkey.co.uk: Post SMTP email error’ which means emails arent being sent from the contact form.

The websites is hosted on siteground and the clients emails are on heart internet.

I’ve run a diagnostics test which has come up with the following:

Mailer: postsmtp
HostName: dreamkey.co.uk
cURL Version: 7.66.0
OpenSSL Version: OpenSSL/1.1.1k-fips
OS: Linux gukm1044.siteground.biz 3.12.18-clouder0 #1 SMP PREEMPT Mon Sep 21 14:18:04 EEST 2020 x86_64
PHP: Linux 7.3.27 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=No, zlib_encode=Yes
WordPress: 5.7 en_US UTF-8
WordPress Theme: Divi
WordPress Plugins: Classic Editor, GDPR Cookie Consent, Duplicate Page, Duplicator, Post SMTP, SG Optimizer, WordPress Importer, Yoast SEO
WordPress wp_mail Owner: /home/customer/www/dreamkey.co.uk/public_html/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email, PostsmtpMailer->get_mail_args
WordPress phpmailer_init Action(s): PostsmtpMailer->phpmailer_smtp_init
Postman: 2.0.22
Postman Sender Domain (Envelope|Message): dreamkey.co.uk | dreamkey.co.uk
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: SMTP (smtp:none:plain://dreamkey.co.uk:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 0 | 75

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