diff --git a/application/libraries/Email_messages.php b/application/libraries/Email_messages.php
index 6a005ee1..ebe40f3c 100644
--- a/application/libraries/Email_messages.php
+++ b/application/libraries/Email_messages.php
@@ -11,6 +11,10 @@
  * @since       v1.4.0
  * ---------------------------------------------------------------------------- */
 
+use PHPMailer\PHPMailer\PHPMailer;
+use PHPMailer\PHPMailer\SMTP;
+use PHPMailer\PHPMailer\Exception;
+
 /**
  * Email messages library.
  *
@@ -59,6 +63,8 @@ class Email_messages
      * @param string $ics_stream ICS file contents.
      * @param string|null $timezone Custom timezone.
      *
+     * @throws DateInvalidTimeZoneException
+     * @throws DateMalformedStringException
      * @throws Exception
      */
     public function send_appointment_saved(
@@ -106,27 +112,18 @@ class Email_messages
             true,
         );
 
-        $from_name = config('from_name') ?: $settings['company_name'];
-        $from_address = config('from_address') ?: $settings['company_email'];
-        $reply_to = config('reply_to') ?: $settings['company_email'];
+        $php_mailer = $this->get_php_mailer();
 
-        $this->CI->email->from($from_address, $from_name);
+        $php_mailer->addAddress($recipient_email);
 
-        if ($reply_to) {
-            $this->CI->email->reply_to($reply_to);
-        }
+        $php_mailer->isHTML();
+        $php_mailer->Subject = $subject;
+        $php_mailer->Body = $html;
+        $php_mailer->AltBody = $html;
 
-        $this->CI->email->to($recipient_email);
+        $php_mailer->addStringAttachment($ics_stream, 'invitation.ics', PHPMailer::ENCODING_BASE64, 'text/vcalendar');
 
-        $this->CI->email->subject($subject);
-
-        $this->CI->email->message($html);
-
-        $this->CI->email->attach($ics_stream, 'attachment', 'invitation.ics', 'text/vcalendar');
-
-        if (!$this->CI->email->send(false)) {
-            throw new RuntimeException('Email was not sent: ' . $this->CI->email->print_debugger());
-        }
+        $php_mailer->send();
     }
 
     /**
@@ -141,6 +138,8 @@ class Email_messages
      * @param string|null $reason Removal reason.
      * @param string|null $timezone Custom timezone.
      *
+     * @throws DateInvalidTimeZoneException
+     * @throws DateMalformedStringException
      * @throws Exception
      */
     public function send_appointment_deleted(
@@ -183,25 +182,18 @@ class Email_messages
             true,
         );
 
-        $from_name = config('from_name') ?: $settings['company_name'];
-        $from_address = config('from_address') ?: $settings['company_email'];
-        $reply_to = config('reply_to') ?: $settings['company_email'];
+        $subject = lang('appointment_cancelled_title');
 
-        $this->CI->email->from($from_address, $from_name);
+        $php_mailer = $this->get_php_mailer();
 
-        if ($reply_to) {
-            $this->CI->email->reply_to($reply_to);
-        }
+        $php_mailer->addAddress($recipient_email);
 
-        $this->CI->email->to($recipient_email);
+        $php_mailer->isHTML();
+        $php_mailer->Subject = $subject;
+        $php_mailer->Body = $html;
+        $php_mailer->AltBody = $html;
 
-        $this->CI->email->subject(lang('appointment_cancelled_title'));
-
-        $this->CI->email->message($html);
-
-        if (!$this->CI->email->send(false)) {
-            throw new RuntimeException('Email was not sent: ' . $this->CI->email->print_debugger());
-        }
+        $php_mailer->send();
     }
 
     /**
@@ -210,6 +202,8 @@ class Email_messages
      * @param string $password New password.
      * @param string $recipient_email Recipient email address.
      * @param array $settings App settings.
+     *
+     * @throws Exception
      */
     public function send_password(string $password, string $recipient_email, array $settings): void
     {
@@ -223,24 +217,50 @@ class Email_messages
             true,
         );
 
-        $from_name = config('from_name') ?: $settings['company_name'];
-        $from_address = config('from_address') ?: $settings['company_email'];
-        $reply_to = config('reply_to') ?: $settings['company_email'];
+        $subject = lang('new_account_password');
 
-        $this->CI->email->from($from_address, $from_name);
+        $php_mailer = $this->get_php_mailer();
 
-        if ($reply_to) {
-            $this->CI->email->reply_to($reply_to);
+        $php_mailer->addAddress($recipient_email);
+
+        $php_mailer->isHTML();
+        $php_mailer->Subject = $subject;
+        $php_mailer->Body = $html;
+        $php_mailer->AltBody = $html;
+
+        $php_mailer->send();
+    }
+
+    /**
+     * Create PHP Mailer instance based on the email configuration.
+     *
+     * @return PHPMailer
+     *
+     * @throws Exception
+     */
+    private function get_php_mailer(): PHPMailer
+    {
+        $php_mailer = new PHPMailer(true);
+
+        $php_mailer->SMTPDebug = config('smtp_debug') ? SMTP::DEBUG_SERVER : null;
+
+        if (config('protocol') === 'smtp') {
+            $php_mailer->isSMTP();
+            $php_mailer->Host = config('smtp_host');
+            $php_mailer->SMTPAuth = config('smtp_auth');
+            $php_mailer->Username = config('smtp_user');
+            $php_mailer->Password = config('smtp_pass');
+            $php_mailer->SMTPSecure = config('smtp_crypto');
+            $php_mailer->Port = config('smtp_port');
         }
 
-        $this->CI->email->to($recipient_email);
+        $from_name = config('from_name') ?: setting('company_name');
+        $from_address = config('from_address') ?: setting('company_email');
+        $reply_to_address = config('reply_to') ?: setting('company_email');
 
-        $this->CI->email->subject(lang('new_account_password'));
+        $php_mailer->setFrom($from_address, $from_name);
+        $php_mailer->addReplyTo($reply_to_address);
 
-        $this->CI->email->message($html);
-
-        if (!$this->CI->email->send(false)) {
-            throw new RuntimeException('Email was not sent: ' . $this->CI->email->print_debugger());
-        }
+        return $php_mailer;
     }
 }
diff --git a/composer.json b/composer.json
index b3671a9d..7025781c 100644
--- a/composer.json
+++ b/composer.json
@@ -42,7 +42,8 @@
         "guzzlehttp/guzzle": "^7.5.0",
         "sabre/vobject": "^4.5",
         "ezyang/htmlpurifier": "^4.17",
-        "symfony/finder": "^6.4"
+        "symfony/finder": "^6.4",
+        "phpmailer/phpmailer": "^6.9"
     },
     "require-dev": {
         "roave/security-advisories": "dev-master",
diff --git a/composer.lock b/composer.lock
index 32ba04e8..96dbc869 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "1600e731726d98eb3e9b5c299cdf108e",
+    "content-hash": "dbf5da5fb7080dd1067d78bcc8625e2d",
     "packages": [
         {
             "name": "ezyang/htmlpurifier",
@@ -956,6 +956,87 @@
             },
             "time": "2020-10-15T08:29:30+00:00"
         },
+        {
+            "name": "phpmailer/phpmailer",
+            "version": "v6.9.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/PHPMailer/PHPMailer.git",
+                "reference": "a7b17b42fa4887c92146243f3d2f4ccb962af17c"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/PHPMailer/PHPMailer/zipball/a7b17b42fa4887c92146243f3d2f4ccb962af17c",
+                "reference": "a7b17b42fa4887c92146243f3d2f4ccb962af17c",
+                "shasum": ""
+            },
+            "require": {
+                "ext-ctype": "*",
+                "ext-filter": "*",
+                "ext-hash": "*",
+                "php": ">=5.5.0"
+            },
+            "require-dev": {
+                "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
+                "doctrine/annotations": "^1.2.6 || ^1.13.3",
+                "php-parallel-lint/php-console-highlighter": "^1.0.0",
+                "php-parallel-lint/php-parallel-lint": "^1.3.2",
+                "phpcompatibility/php-compatibility": "^9.3.5",
+                "roave/security-advisories": "dev-latest",
+                "squizlabs/php_codesniffer": "^3.7.2",
+                "yoast/phpunit-polyfills": "^1.0.4"
+            },
+            "suggest": {
+                "decomplexity/SendOauth2": "Adapter for using XOAUTH2 authentication",
+                "ext-mbstring": "Needed to send email in multibyte encoding charset or decode encoded addresses",
+                "ext-openssl": "Needed for secure SMTP sending and DKIM signing",
+                "greew/oauth2-azure-provider": "Needed for Microsoft Azure XOAUTH2 authentication",
+                "hayageek/oauth2-yahoo": "Needed for Yahoo XOAUTH2 authentication",
+                "league/oauth2-google": "Needed for Google XOAUTH2 authentication",
+                "psr/log": "For optional PSR-3 debug logging",
+                "symfony/polyfill-mbstring": "To support UTF-8 if the Mbstring PHP extension is not enabled (^1.2)",
+                "thenetworg/oauth2-azure": "Needed for Microsoft XOAUTH2 authentication"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "PHPMailer\\PHPMailer\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "LGPL-2.1-only"
+            ],
+            "authors": [
+                {
+                    "name": "Marcus Bointon",
+                    "email": "phpmailer@synchromedia.co.uk"
+                },
+                {
+                    "name": "Jim Jagielski",
+                    "email": "jimjag@gmail.com"
+                },
+                {
+                    "name": "Andy Prevost",
+                    "email": "codeworxtech@users.sourceforge.net"
+                },
+                {
+                    "name": "Brent R. Matzelle"
+                }
+            ],
+            "description": "PHPMailer is a full-featured email creation and transfer class for PHP",
+            "support": {
+                "issues": "https://github.com/PHPMailer/PHPMailer/issues",
+                "source": "https://github.com/PHPMailer/PHPMailer/tree/v6.9.2"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/Synchro",
+                    "type": "github"
+                }
+            ],
+            "time": "2024-10-09T10:07:50+00:00"
+        },
         {
             "name": "phpseclib/phpseclib",
             "version": "3.0.37",