rookas

Tim, changed to “login”, but no difference:

Mailer: postsmtp
HostName: ggunique.com
cURL Version: 7.71.0
OpenSSL Version: OpenSSL/1.1.1d
OS: Linux lt-bnk-web182.main-hosting.eu 3.10.0-962.3.2.lve1.5.25.10.el7.x86_64 #1 SMP Wed May 29 04:37:40 EDT 2019 x86_64
PHP: Linux 7.2.34 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: Shop Isle
WordPress Plugins: Query Monitor, Advanced Product Fields for WooCommerce, Akismet Anti-Spam, Autoptimize, SEO Control Center, Cookie Notice & Compliance for GDPR / CCPA, Easy Theme and Plugin Upgrades, Estonian Shipping Methods for WooCommerce, Facebook for WooCommerce, Flexible Shipping, Global Site Tag Tracking, Google Analytics for WordPress by MonsterInsights, Insert Headers and Footers, Jetpack by WordPress.com, “LP Express” Shipping Method for WooCommerce, Mailchimp for WooCommerce, MultiParcels Shipping For WooCommerce, Post SMTP, PW WooCommerce Gift Cards, SmartCrawl, SiteOrigin CSS, Orbit Fox Companion, TranslatePress – Multilingual, Under Construction, WooCommerce Cart Abandonment Recovery, Checkout Field Editor for WooCommerce, Advanced Order Export For WooCommerce, WooCommerce Payment Gateway – Paysera, WooCommerce Shipping – DPD baltic, WooCommerce PayPal Checkout Gateway, WooCommerce PDF Invoices & Packing Slips, WooCommerce Shipping & Tax, WooCommerce, Wordfence Security, Yoast SEO, WP phpMyAdmin, WP Sitemap Page, WP Super Cache, WPForms Lite
WordPress wp_mail Owner: /home/u799333977/domains/ggunique.com/public_html/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): TRP_Translation_Render->wp_mail_filter, wp_staticize_emoji_for_email, WPO\WC\PDF_Invoices\Main->set_phpmailer_validator, PostsmtpMailer->get_mail_args
WordPress wp_mail_from Filter(s): wordfence::fixWPMailFromAddress
WordPress phpmailer_init Action(s): PostsmtpMailer->phpmailer_smtp_init
Postman: 2.0.22
Postman Sender Domain (Envelope|Message): ggunique.com | ggunique.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: SMTP (smtp:tls:login://smtp.zoho.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 6535 | 188

yes, just did that again, but no change.

Also troubleshooting data added:

Mailer: postsmtp
HostName: ggunique.com
cURL Version: 7.71.0
OpenSSL Version: OpenSSL/1.1.1d
OS: Linux lt-bnk-web182.main-hosting.eu 3.10.0-962.3.2.lve1.5.25.10.el7.x86_64 #1 SMP Wed May 29 04:37:40 EDT 2019 x86_64
PHP: Linux 7.2.34 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: Shop Isle
WordPress Plugins: Query Monitor, Advanced Product Fields for WooCommerce, Akismet Anti-Spam, Autoptimize, SEO Control Center, Cookie Notice & Compliance for GDPR / CCPA, Easy Theme and Plugin Upgrades, Estonian Shipping Methods for WooCommerce, Facebook for WooCommerce, Flexible Shipping, Global Site Tag Tracking, Google Analytics for WordPress by MonsterInsights, Insert Headers and Footers, Jetpack by WordPress.com, "LP Express" Shipping Method for WooCommerce, Mailchimp for WooCommerce, MultiParcels Shipping For WooCommerce, Post SMTP, PW WooCommerce Gift Cards, SmartCrawl, SiteOrigin CSS, Orbit Fox Companion, TranslatePress - Multilingual, Under Construction, WooCommerce Cart Abandonment Recovery, Checkout Field Editor for WooCommerce, Advanced Order Export For WooCommerce, WooCommerce Payment Gateway - Paysera, WooCommerce Shipping - DPD baltic, WooCommerce PayPal Checkout Gateway, WooCommerce PDF Invoices & Packing Slips, WooCommerce Shipping & Tax, WooCommerce, Wordfence Security, Yoast SEO, WP phpMyAdmin, WP Sitemap Page, WP Super Cache, WPForms Lite
WordPress wp_mail Owner: /home/u799333977/domains/ggunique.com/public_html/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): TRP_Translation_Render->wp_mail_filter, wp_staticize_emoji_for_email, WPO\WC\PDF_Invoices\Main->set_phpmailer_validator, PostsmtpMailer->get_mail_args
WordPress wp_mail_from Filter(s): wordfence::fixWPMailFromAddress
WordPress phpmailer_init Action(s): PostsmtpMailer->phpmailer_smtp_init
Postman: 2.0.22
Postman Sender Domain (Envelope|Message): ggunique.com | ggunique.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: SMTP (smtp:tls:plain://smtp.zoho.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 6535 | 186

Here is the diagnostic test output:

Mailer: postsmtp
HostName: ggunique.com
cURL Version: 7.71.0
OpenSSL Version: OpenSSL/1.1.1d
OS: Linux lt-bnk-web182.main-hosting.eu 3.10.0-962.3.2.lve1.5.25.10.el7.x86_64 #1 SMP Wed May 29 04:37:40 EDT 2019 x86_64
PHP: Linux 7.2.34 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: Shop Isle
WordPress Plugins: Query Monitor, Advanced Product Fields for WooCommerce, Akismet Anti-Spam, Autoptimize, SEO Control Center, Cookie Notice & Compliance for GDPR / CCPA, Easy Theme and Plugin Upgrades, Estonian Shipping Methods for WooCommerce, Facebook for WooCommerce, Flexible Shipping, Global Site Tag Tracking, Google Analytics for WordPress by MonsterInsights, Insert Headers and Footers, Jetpack by WordPress.com, "LP Express" Shipping Method for WooCommerce, Mailchimp for WooCommerce, MultiParcels Shipping For WooCommerce, Post SMTP, PW WooCommerce Gift Cards, SmartCrawl, SiteOrigin CSS, Orbit Fox Companion, TranslatePress - Multilingual, Under Construction, WooCommerce Cart Abandonment Recovery, Checkout Field Editor for WooCommerce, Advanced Order Export For WooCommerce, WooCommerce Payment Gateway - Paysera, WooCommerce Shipping - DPD baltic, WooCommerce PayPal Checkout Gateway, WooCommerce PDF Invoices & Packing Slips, WooCommerce Shipping & Tax, WooCommerce, Wordfence Security, Yoast SEO, WP phpMyAdmin, WP Sitemap Page, WP Super Cache
WordPress wp_mail Owner: /home/u799333977/domains/ggunique.com/public_html/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php
WordPress wp_mail Filter(s): TRP_Translation_Render->wp_mail_filter, wp_staticize_emoji_for_email, WPO\WC\PDF_Invoices\Main->set_phpmailer_validator, PostsmtpMailer->get_mail_args
WordPress wp_mail_from Filter(s): wordfence::fixWPMailFromAddress
WordPress phpmailer_init Action(s): PostsmtpMailer->phpmailer_smtp_init
Postman: 2.0.22
Postman Sender Domain (Envelope|Message): ggunique.com | ggunique.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: SMTP (smtp:tls:plain://smtp.zoho.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 6535 | 181

220 mx.zohomail.com SMTP Server ready March 24, 2021 9:15:59 AM PDT
EHLO ggunique.com
250-mx.zohomail.com Hello ggunique.com (46.17.175.36 (46.17.175.36))
250-STARTTLS
250 SIZE 32505856
STARTTLS
220 Ready to start TLS.
EHLO ggunique.com
250-mx.zohomail.com Hello ggunique.com (46.17.175.36 (46.17.175.36))
250-AUTH LOGIN PLAIN
250 SIZE 32505856
AUTH PLAIN
334
AGluZm9AZ2d1bmlxdWUuY29tAGdvYmFieWdvODg=
535 Authentication Failed

Updated theme to ShopIsle (1.1.62) and now everything works.