Redigit

Emerge Mail replaces SMTP plugins for transactional WordPress email. Connect one or more mail accounts and every <code>wp_mail()</code> call your site makes — password resets, comment notifications, WooCommerce receipts, contact-form submissions — is delivered through that account.
Seven providers, one unified send path:
<ul>
<li>Gmail (OAuth) — sign in to your Google account; no SMTP password needed.</li>
<li>Microsoft 365 / Outlook (OAuth) — sign in to personal Outlook/Hotmail/Live or Microsoft 365 work/school accounts.</li>
<li>SendGrid (API key) — paste a v3 API key with Mail Send permission.</li>
<li>Mailgun (API key) — paste a private API key, sending domain, and pick your region (US or EU).</li>
<li>Amazon SES (Sigv4) — paste an IAM access key + secret with <code>ses:SendEmail</code> permission. No AWS SDK dependency.</li>
<li>Brevo (API key) — paste a v3 API key.</li>
<li>Generic SMTP — host + port + encryption + username + password for any SMTP server (your own host, an SES SMTP endpoint, Postmark SMTP, Fastmail, mailcow, etc.).</li>
</ul>
Because the From address is your own authenticated mailbox or verified sender, messages benefit from SPF, DKIM, and DMARC alignment that PHP’s <code>mail()</code> function cannot provide. This typically results in dramatically better inbox placement than default WordPress mail.
<h4>Key features</h4>
<ul>
<li>Seven providers (above), all sharing the same routing, failover, and From-email overrides.</li>
<li>Multiple connections per site with automatic failover. The Active connection sends first; if it fails, the next available connection is tried, with a 10-minute cooldown on failed connections. Mix-and-match across providers — e.g. SendGrid primary, an SMTP fallback, and a Gmail mailbox as the last-resort backup.</li>
<li>Optional bulk-send throttle: when a burst of sends is detected, rotate through your connected accounts instead of hammering the Active one.</li>
<li>Per-connection From email override for verified send-as aliases / verified senders.</li>
<li>Configurable sender defaults: a custom From name and an opt-in “Reply-To = admin email when sender differs” setting.</li>
<li>Full <code>wp_mail</code> compatibility: To/Cc/Bcc (including from headers), HTML bodies, multipart alternative, attachments, custom headers, RFC 2822 address formats including comma-separated lists and quoted display names, non-UTF-8 charsets.</li>
<li>RFC 2047 encoding for non-ASCII subjects and display names.</li>
<li>One-click Send test button per connection.</li>
<li>Email Controls page: opt-in suppression of WordPress core self-notifications you don’t want to receive (comment moderation, automatic updates, new-user registered, etc.) — recorded to the Activity Log instead.</li>
<li>Activity Log page: unified record of suppressed notifications, provider send errors, and recipient bounces — with type and severity filters, bulk delete, and automatic 30-day pruning.</li>
<li>Bounce classification: provider-specific error patterns map to a unified <code>send.bounce.*</code> / <code>send.error.*</code> taxonomy so per-recipient bounces are distinguished from transport outages across all seven providers.</li>
<li>Last-error visibility per connection and a site-wide admin notice on recent failures.</li>
<li>Automatic hourly token refresh for OAuth connections (Action Scheduler when available, WP-Cron fallback). API-key connections require no maintenance.</li>
<li>Safe fallback to default WordPress mail delivery on any failure — the plugin never blocks email.</li>
<li>Extensible via filters: cooldown, bulk thresholds, HTTP timeouts, token-refresh timing, MIME output, suppression catalog.</li>
</ul>
<h4>How it works</h4>
When you connect an account, the credentials (OAuth tokens, or your API key / SMTP password) are encrypted with a per-site key and stored as a WordPress option. From that point on, your site talks directly to the provider’s API or SMTP endpoint; no third party sits in the send path.
The plugin hooks <code>pre_wp_mail</code>. If at least one connection is active, the message is routed through it. If the provider returns an error — or if no connections are configured — WordPress’s default mail delivery takes over transparently.
<h4>What this is not</h4>
<ul>
<li>Not a marketing or bulk email tool. No subscriber lists, no campaigns, no broadcasts.</li>
<li>Not a shared-IP SMTP relay. Each site sends from its own connected accounts.</li>
<li>Not a way to spoof arbitrary From addresses. The provider will reject anything that isn’t an authorized sender on the connected account.</li>
</ul>
<h3>External services</h3>
To deliver mail, Emerge Mail can communicate with up to eight external services depending on which providers you connect. An optional ninth service (anonymous usage reporting) is off by default and only activated when the operator explicitly opts in. By installing and using this plugin you agree to use of these services. Nothing is contacted until you connect at least one provider in the plugin settings — every external call below is gated on the corresponding connection existing or the telemetry toggle being enabled.
<h4>1. Emerge OAuth service (emerge.redigit.net)</h4>
What it is and what it’s used for: A stateless OAuth proxy operated by the plugin author. It exists to broker the OAuth authorization handshake between your WordPress site and Google or Microsoft so the plugin can be authorized to send mail from your mailbox. The proxy holds the OAuth client secrets that Google and Microsoft would otherwise require every site to register individually.
What data is sent, when:
<ul>
<li>When you click Connect Gmail or Connect Microsoft, your browser is redirected to <code>https://emerge.redigit.net/oauth/{provider}/authorize</code> with a PKCE code challenge and a state token generated by your site. No personal data is sent.</li>
<li>When the provider redirects back, your site posts the authorization code and PKCE verifier to <code>https://emerge.redigit.net/oauth/{provider}/token</code> to receive the access and refresh tokens. The tokens are returned directly to your site and stored locally, encrypted, in <code>wp_options</code>. The proxy does not persist them.</li>
<li>When an access token nears expiry, your site posts the refresh token to <code>https://emerge.redigit.net/oauth/{provider}/refresh</code> to obtain a new access token. Again, nothing is persisted on the proxy.</li>
<li>No email content, recipient lists, or message metadata is ever sent to the proxy.</li>
</ul>
Terms and privacy:
<ul>
<li>Terms of Service: <a href="https://emerge.redigit.net/terms-of-service" rel="nofollow ugc">https://emerge.redigit.net/terms-of-service</a></li>
<li>Privacy Policy: <a href="https://emerge.redigit.net/privacy-policy" rel="nofollow ugc">https://emerge.redigit.net/privacy-policy</a></li>
</ul>
<h4>2. Google APIs (Gmail)</h4>
What it is and what it’s used for: Used only when you connect a Gmail mailbox. Once authorized, the plugin sends every <code>wp_mail()</code> message directly to the Gmail API (<code>gmail.googleapis.com</code>) from your WordPress site. Periodically the plugin also calls the Google OAuth userinfo endpoint (<code>www.googleapis.com/oauth2/v2/userinfo</code>) to verify the access token is still valid.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a Gmail connection: the full outbound message (To/Cc/Bcc, subject, body, attachments, custom headers) is POSTed to <code>https://gmail.googleapis.com/gmail/v1/users/me/messages/send</code> as a base64-encoded RFC822 message. This is what’s required for the message to reach the recipient.</li>
<li>On token validation: a Bearer token is sent to <code>https://www.googleapis.com/oauth2/v2/userinfo</code>. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>Google Terms of Service: <a href="https://policies.google.com/terms" rel="nofollow ugc">https://policies.google.com/terms</a></li>
<li>Google Privacy Policy: <a href="https://policies.google.com/privacy" rel="nofollow ugc">https://policies.google.com/privacy</a></li>
<li>Google API Services User Data Policy: <a href="https://developers.google.com/terms/api-services-user-data-policy" rel="nofollow ugc">https://developers.google.com/terms/api-services-user-data-policy</a></li>
</ul>
<h4>3. Microsoft Graph (Outlook / Microsoft 365)</h4>
What it is and what it’s used for: Used only when you connect a Microsoft mailbox. Once authorized, the plugin sends every <code>wp_mail()</code> message directly to Microsoft Graph (<code>graph.microsoft.com</code>) from your WordPress site. Periodically the plugin also calls Graph’s <code>/me</code> endpoint to verify the access token is still valid.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a Microsoft connection: the full outbound message (To/Cc/Bcc, subject, body, attachments, custom headers) is POSTed to <code>https://graph.microsoft.com/v1.0/me/sendMail</code> as a JSON payload. This is what’s required for the message to reach the recipient.</li>
<li>On token validation: a Bearer token is sent to <code>https://graph.microsoft.com/v1.0/me</code>. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>Microsoft Services Agreement: <a href="https://www.microsoft.com/en/servicesagreement" rel="nofollow ugc">https://www.microsoft.com/en/servicesagreement</a></li>
<li>Microsoft Privacy Statement: <a href="https://privacy.microsoft.com/en-us/privacystatement" rel="nofollow ugc">https://privacy.microsoft.com/en-us/privacystatement</a></li>
</ul>
<h4>4. SendGrid (api.sendgrid.com)</h4>
What it is and what it’s used for: Used only when you add a SendGrid connection. The plugin sends every <code>wp_mail()</code> message routed through that connection directly to the SendGrid Mail Send API. The connect-time validation also calls SendGrid’s <code>/v3/user/profile</code> to confirm the API key works.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a SendGrid connection: the outbound message (recipients, subject, body, attachments, custom headers) is POSTed to <code>https://api.sendgrid.com/v3/mail/send</code> as a JSON payload.</li>
<li>On connect: an authenticated GET is sent to <code>https://api.sendgrid.com/v3/user/profile</code> to validate the API key. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>SendGrid Terms: <a href="https://www.twilio.com/legal/tos" rel="nofollow ugc">https://www.twilio.com/legal/tos</a></li>
<li>SendGrid Privacy Statement: <a href="https://www.twilio.com/legal/privacy" rel="nofollow ugc">https://www.twilio.com/legal/privacy</a></li>
</ul>
<h4>5. Mailgun (api.mailgun.net or api.eu.mailgun.net)</h4>
What it is and what it’s used for: Used only when you add a Mailgun connection. The plugin sends every <code>wp_mail()</code> message routed through that connection directly to the Mailgun Messages API on the region (US or EU) you select at connect time.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a Mailgun connection: the outbound message (recipients, subject, body, attachments, custom headers) is POSTed as multipart/form-data to <code>https://api.mailgun.net/v3/{your-domain}/messages</code> (or the EU equivalent).</li>
<li>On connect: an authenticated GET is sent to <code>/v3/domains/{your-domain}</code> to validate the API key + domain pairing. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>Mailgun Terms of Service: <a href="https://www.mailgun.com/legal/terms/" rel="nofollow ugc">https://www.mailgun.com/legal/terms/</a></li>
<li>Mailgun Privacy Policy: <a href="https://www.mailgun.com/legal/privacy-policy/" rel="nofollow ugc">https://www.mailgun.com/legal/privacy-policy/</a></li>
</ul>
<h4>6. Amazon SES (email.{region}.amazonaws.com)</h4>
What it is and what it’s used for: Used only when you add an Amazon SES connection. The plugin sends every <code>wp_mail()</code> message routed through that connection directly to the SES v2 SendEmail API in the AWS region you select at connect time. Requests are signed with AWS Signature V4 using the IAM credentials you provided.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a SES connection: the outbound message (recipients, subject, body, custom headers) is POSTed to <code>https://email.{region}.amazonaws.com/v2/email/outbound-emails</code> as a JSON payload.</li>
<li>On connect: a signed GET is sent to <code>/v2/email/account</code> in the same region to validate the credentials. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>AWS Customer Agreement: <a href="https://aws.amazon.com/agreement/" rel="nofollow ugc">https://aws.amazon.com/agreement/</a></li>
<li>AWS Privacy Notice: <a href="https://aws.amazon.com/privacy/" rel="nofollow ugc">https://aws.amazon.com/privacy/</a></li>
</ul>
<h4>7. Brevo (api.brevo.com)</h4>
What it is and what it’s used for: Used only when you add a Brevo connection. The plugin sends every <code>wp_mail()</code> message routed through that connection directly to the Brevo Transactional Email API.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through a Brevo connection: the outbound message (recipients, subject, body, attachments, custom headers) is POSTed to <code>https://api.brevo.com/v3/smtp/email</code> as a JSON payload.</li>
<li>On connect: an authenticated GET is sent to <code>https://api.brevo.com/v3/account</code> to validate the API key. No message data is included.</li>
</ul>
Terms and privacy:
<ul>
<li>Brevo Terms of Use: <a href="https://www.brevo.com/legal/termsofuse/" rel="nofollow ugc">https://www.brevo.com/legal/termsofuse/</a></li>
<li>Brevo Privacy Policy: <a href="https://www.brevo.com/legal/privacypolicy/" rel="nofollow ugc">https://www.brevo.com/legal/privacypolicy/</a></li>
</ul>
<h4>8. Your own SMTP server (Generic SMTP)</h4>
What it is and what it’s used for: Used only when you add a Generic SMTP connection. The plugin opens an SMTP connection to whatever host:port you specify, authenticates with the username and password you provide, and sends <code>wp_mail()</code> messages via SMTP. WordPress’s bundled PHPMailer library handles the SMTP protocol.
What data is sent, when:
<ul>
<li>On each <code>wp_mail()</code> call routed through this connection: the outbound message (recipients, subject, body, attachments, custom headers) is transmitted over SMTP to your configured host.</li>
<li>On connect: PHPMailer opens the SMTP connection, runs EHLO + STARTTLS (if enabled), and authenticates — no message is sent.</li>
</ul>
Terms and privacy: Determined by whichever SMTP server you choose to connect to. This plugin does not introduce any third-party SMTP relay; you control the destination.

Emerge Mail

Route wp_mail through Gmail, Microsoft, SendGrid, Mailgun, Amazon SES, Brevo, or any SMTP server. OAuth or bring-your-own-key, with multi-mailbox fail …

Surbma

CherryPick Studios

This plugin is created especially for Multisite Networks. You can define all variables in the wp-config.php file and it will be valid for all sites in a Multisite. So this is not for a site-by-site configuration plugin. You can install it on a single WordPress install also and it will work perfectly. But if you install it in a Multisite Network, you can only network activate it!
This plugin is working with all SMTP servers and services, like Mailgun, SendGrid, Mandrill, Amazon SES and others.
Required variables:
<ul>
<li><code>SURBMA_SMTP_HOST</code> – External SMTP server.</li>
<li><code>SURBMA_SMTP_USER</code> – User for the SMTP account.</li>
<li><code>SURBMA_SMTP_PASSWORD</code> – Password for the SMTP account.</li>
</ul>
Optional variables:
<ul>
<li><code>SURBMA_SMTP_PORT</code> – Port number for the SMTP server.</li>
<li><code>SURBMA_SMTP_SECURE</code> – Choose SSL or TLS, if necessary for your SMTP server.</li>
<li><code>SURBMA_SMTP_FROM</code> – From email address for all outgoing emails.</li>
<li><code>SURBMA_SMTP_FROMNAME</code> – From name for all outgoing emails.</li>
</ul>
Example configuration:
<pre><code> define('SURBMA_SMTP_HOST','smtp.mailgun.org');
 define('SURBMA_SMTP_USER','postmaster@surbma.com');
 define('SURBMA_SMTP_PASSWORD','bb2b************************4133');
</code></pre>
You can put these lines everywhere before the line, that says: “That’s It. Pencils down”
Do you want to contribute or help improving this plugin?
You can find it on GitHub: <a href="https://github.com/Surbma/surbma-smtp" rel="nofollow ugc">https://github.com/Surbma/surbma-smtp</a>
You can find my other plugins and projects on GitHub:
<a href="https://github.com/Surbma" rel="nofollow ugc">https://github.com/Surbma</a>
Please feel free to contribute, help or recommend any new features for my plugins, themes and other projects.
Do you want to know more about me?
Visit my webpage: <a href="http://surbma.com/" rel="nofollow ugc">Surbma.com</a>

Surbma | SMTP

External SMTP mail configuration via global variables in wp-config.php.

Emerge Mail vs Surbma | SMTP