Sending emails not working

Hi,

In the last couple of weeks our emails have stopped working through Postman SMPT and we can’t work out why. We have just discovered the issue this week. Can you please assist? This is urgent as it is affecting our business.

We did change the Outgoing Mail Server Hostname and email address in February 2021 but it had been working fine until recently. When someone fills out our enquiry form (https://www.horner.com.au/enquiry-form/) normally an email is sent from our website to our sales team to notify us. This email has stopped working. Because of this people are currently unable to actually “submit” on the enquiry form and comes up with an error message “There was an error trying to send your message. Please try again later.” The info from the enquiry form is actually going into our contact Database but the email notification to us is not working.

We also send emails to candidates in the form of job alert notifications from our website and these are not sending either.

In the email log the status for the emails says “Unable to connect via TLS”.
I have tried to send test emails and says “Failed” with the message “Unable to connect via TLS”.

Why have the emails suddenly stopped working and how can we urgently fix it?

Diagnostic report below:

OS: Linux c5s4-3e-syd.hosting-services.net.au 2.6.32-954.3.5.lve1.4.63.el6.x86_64 #1 SMP Sun Apr 7 10:18:40 EDT 2019 x86_64
PHP: Linux 5.6.40 C
PHP Dependencies: iconv=Yes, spl_autoload=Yes, openssl=Yes, sockets=Yes, allow_url_fopen=Yes, mcrypt=Yes, zlib_encode=Yes
WordPress: 4.9.7 en_AU UTF-8
WordPress Theme: Harry Ta
WordPress Plugins: Advanced Custom Fields PRO, BackWPup, Honeypot for Contact Form 7, Contact Form DB, Contact Form 7, Corona Virus (COVID-19) Banner & Live Data, CoSchedule, Duplicator, Insert Headers and Footers, HubSpot All-In-One Marketing – Forms, Popups, Live Chat, LoginPress – Customizing the WordPress Login, Postman SMTP, Redirection, Regenerate Thumbnails, Simple Banner, Simple Page Ordering, SumoMe, Category Order and Taxonomy Terms Order, WP Team, TinyMCE Advanced, TinyMCE and TinyMCE Advanced Professsional Formats and Styles, W3 Total Cache, Yoast SEO, WP Downgrade | Specific Core Version, WP Job Manager – Alerts, WP Job Manager – Bookmarks, WP Job Manager Integration with Idibu, WP Job Manager, Smush, WP Job Manager addon – Jobs Geolocation, WP Stagecoach
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
WordPress wp_mail_content_type Filter(s): set_content_type_html
WordPress phpmailer_init Action(s): wpcf7_phpmailer_init
Postman: 1.7.2
Postman Sender Domain (Envelope|Message): horner.com.au | horner.com.au
Postman Prevent Message Sender Override (Email|Name): Yes | Yes
Postman Active Transport: SMTP (smtp:tls:login://au-smtp-outbound-1.mimecast.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 1072 | 278
Postman Email Log (Enabled|Limit|Transcript Size): Yes | 2000 | 128

Thanks in advance for your reply and assistance.

thanks
Shelley

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