Email Essentials

Important Note

This tool is for users who understand email delivery. If unsure, ask for help.

Under GDPR, storing and tracking emails is prohibited. The history feature is for investigative purposes only!

External services

Email Essentials uses one external service by default, two if you create and define your own IP services.

1. 01CloudFlare DNS over HTTPS (DoH). This is used to resolve domain names to IP addresses when (for example) checking SPF or DKIM records. In theory, it is possible to use PHPs own dns_get_record function, but in practice this often fails due to server DNS-resolve misconfiguration. Using CloudFlare’s DoH service ensures reliable DNS resolution. We only send the hostname (the domain part) to CloudFlare, no other data. Explicitly, we do NOT send any other information.
2. 02The plugin can use an IP-address relay service to accurately determine the sender’s IP address. This is required to accurately check that the sender’s IP address is authorized to send email for the domain (SPF check). To use this, you will need to set up your own service, see documentation on filter acato_email_essentials_ip_services . Without this service, IP detection can be inaccurate because it will use the website itself as a relay. Use of a reverse proxy, load balancer etc. can lead to incorrect IP detection.

WordPress Filters

• acato_email_essentials_settings — Filter plugin settings.
• acato_email_essentials_defaults — Filter default settings.
• acato_email_essentials_subject — Filter email subject.
• acato_email_essentials_body — Filter HTML body of the email.
• acato_email_essentials_head — Filter HEAD section of HTML email.
• acato_email_essentials_css — Filter CSS for the email.
• acato_email_essentials_minify_css — Filter CSS minification.
• acato_email_essentials_mail_is_throttled — Check if mail should be throttled.
• acato_email_essentials_mail_throttle_time_window — Set mail throttle time window.
• acato_email_essentials_mail_throttle_max_count_per_time_window — Set max emails per time window.
• acato_email_essentials_mail_throttle_batch_size — Set mail batch size.
• acato_email_essentials_ip_services — Define custom IP services for accurately determining the sender’s IP address.
• acato_email_essentials_ip_service — Filter individual IP service URLs.
• acato_email_essentials_spf_patches — Patch SPF lookup to fix false negative detections.
• acato_email_essentials_website_root_path — Filter to supply the correct website root path in case of non-standard setups.
• acato_email_essentials_development_tlds — Filter development/local TLDs.

WordPress Filters in detail

Plugin Settings

acato_email_essentials_settings

Parameters: – (array) $settings The current settings of the plugin.

Expected return: – (array) The new settings of the plugin.

acato_email_essentials_defaults

Parameters: – (array) $defaults The current default settings of the plugin.

Expected return: – (array) The new default settings of the plugin.

Email Content

acato_email_essentials_subject

Parameters: – (string) $the_subject Subject for the email. – (PHPMailer) $mailer The PHPMailer object (by reference).

Expected return: – (string) The (altered) Subject.

acato_email_essentials_body

Parameters: – (string) $should_be_html A text that should be html, but might not yet be, your job to make a nice HTML body. – (PHPMailer) $mailer The PHPMailer object (by reference).

Expected return: – (string) A text that should be html.

acato_email_essentials_head

Parameters: – (string) $the_head_section HTML that is the HEAD section of the HTML email. – (PHPMailer) $mailer The PHPMailer object (by reference).

Expected return: – (string) The altered HEAD section of the HTML email.

acato_email_essentials_css

Parameters: – (string) $the_css CSS for the email (empty by default). – (PHPMailer) $mailer The PHPMailer object (by reference).

Expected return: – (string) The (altered) CSS.

acato_email_essentials_minify_css

Parameters: – (string) $css CSS to be minified.

Expected return: – (string) The minified CSS.

Mail Throttling

acato_email_essentials_mail_is_throttled

Parameters: – (bool) $is_throttled Whether the mail is currently throttled. – (string) $ip The sender’s IP address. – (int) $mails_recently_sent Number of mails recently sent from this IP.

Expected return: – (bool) Whether the mail should be throttled.

acato_email_essentials_mail_throttle_time_window

Parameters: – (int) $time_window Time window in seconds for counting sent emails.

Expected return: – (int) The (altered) time window in seconds.

acato_email_essentials_mail_throttle_max_count_per_time_window

Parameters: – (int) $count Maximum number of emails allowed per time window.

Expected return: – (int) The (altered) maximum count.

acato_email_essentials_mail_throttle_batch_size

Parameters: – (int) $size Number of emails to send in a single batch.

Expected return: – (int) The (altered) batch size.

IP Detection

acato_email_essentials_ip_services

Parameters: – (array) $services The current list of IP services used to determine the sender’s IP address.

Expected return: – (array) The (altered) list of IP services.

The services must be keyed with ipv4 , ipv6 and dual-stack . The values must be URLs that return the IP address in plain text. The dual-stack service should return an IPv6 address if available, otherwise an IPv4 address, never both.

You can set-up your own service like this;

• You will need a webserver that can run PHP, and you need a DNS service that allows you to manually add records.
• You will need three webspaces, for example; ipv4.myservice.com, ipv6.myservice.com and dual-stack.myservice.com. You could use the same webspace for all three, but you will still need three subdomains on the service.

For the ipv4 subdomain, ONLY register an A record, pointing to the webserver’s IP address. For the ipv6 subdomain, ONLY register an AAAA record, pointing to the webserver’s IPv6 address. For the dual-stack subdomain, register both an A and an AAAA record, pointing to the webserver’s IP addresses.

Create a file called index.php in each of the webspaces with the following content:

php <?php header('Content-Type: text/plain'); print $_SERVER['REMOTE_ADDR'];

That’s it. You can now use these services in the plugin settings like this;

`php

add_filter(‘acato_email_essentials_ip_services’, ‘my_custom_ip_services’); function my_custom_ip_services($services) { // Add your custom services here $services[‘ipv4’] = ‘https://ipv4.myservice.com’; $services[‘ipv6’] = ‘https://ipv6.myservice.com’; $services[‘dual-stack’] = ‘https://dual-stack.myservice.com’; return $services; } `

acato_email_essentials_ip_service

Parameters: – (string) $service The URL of the IP service for the given type. – (string) $type The type of IP service (‘ipv4’, ‘ipv6’, or ‘dual-stack’).

Expected return: – (string) The (altered) IP service URL.

Filter to modify individual IP service URLs based on type.

acato_email_essentials_spf_patches

Parameters: – (array) $patches The current SPF patches.

Expected return: – (array) The (altered) SPF patches.

$patches format:

– (array) An associative array where keys are domain names and values are arrays of missing SPF mechanisms. – Array keys are domain names (e.g., ‘spf.example.com’). – Array values are arrays of missing SPF mechanisms (e.g., [‘ip4:1.2.3.4’, ‘ip4:5.6.7.8’]).

When to use: – Use this filter to add missing SPF mechanisms for specific domains, for example when the detected IP for outgoing email is not listed in the officially documented SPF record for that domain. – This is the case for at least one service in the wild as of writing, namely Flowmailer. – The IP Address for smtp.flowmailer.