diff --git a/app/Http/Controllers/ConversationsController.php b/app/Http/Controllers/ConversationsController.php
index b40e12ba..691205dc 100755
--- a/app/Http/Controllers/ConversationsController.php
+++ b/app/Http/Controllers/ConversationsController.php
@@ -753,6 +753,13 @@ class ConversationsController extends Controller
                     }
                 }
 
+                $body = $request->body;
+
+                // Replace base64 images with attachment URLs in case text
+                // was copy and pasted into the editor.
+                // https://github.com/freescout-helpdesk/freescout/issues/3057
+                $body = Thread::replaceBase64ImagesWithAttachments($body);
+
                 // List of emails.
                 $to_array = [];
                 if ($is_forward) {
@@ -789,7 +796,7 @@ class ConversationsController extends Controller
                         $conversation = new Conversation();
                         $conversation->type = $type;
                         $conversation->subject = $request->subject;
-                        $conversation->setPreview($request->body);
+                        $conversation->setPreview($body);
                         $conversation->mailbox_id = $request->mailbox_id;
                         $conversation->created_by_user_id = auth()->user()->id;
                         $conversation->source_via = Conversation::PERSON_USER;
@@ -937,7 +944,7 @@ class ConversationsController extends Controller
                         $conversation->threads_count++;
                         // We need to set preview here as when conversation is created from draft,
                         // ThreadObserver::created() method is not called.
-                        $conversation->setPreview($request->body);
+                        $conversation->setPreview($body);
                     }
                     $conversation->save();
 
@@ -993,7 +1000,7 @@ class ConversationsController extends Controller
                     $thread->created_by_user_id = auth()->user()->id;
                     $thread->edited_by_user_id = null;
                     $thread->edited_at = null;
-                    $thread->body = $request->body;
+                    $thread->body = $body;
                     if ($is_create && !$is_multiple && count($to_array) > 1) {
                         $thread->setTo($to_array);
                     } else {
diff --git a/app/Misc/Helper.php b/app/Misc/Helper.php
index 5e278a8c..8c73058b 100644
--- a/app/Misc/Helper.php
+++ b/app/Misc/Helper.php
@@ -1331,7 +1331,7 @@ class Helper
         $links = array();
 
         // Extract existing links and tags
-        $value = preg_replace_callback('~(<a .*?>.*?</a>|<.*?>)~i', function ($match) use (&$links) { return '<' . array_push($links, $match[1]) . '>'; }, $value ?? '');
+        $value = preg_replace_callback('~(<a .*?>.*?</a>|<.*?>)~i', function ($match) use (&$links) { return '<' . array_push($links, $match[1]) . '>'; }, $value ?? '') ?: $value;
 
         $value = $value ?? '';
 
@@ -1339,14 +1339,17 @@ class Helper
         foreach ((array)$protocols as $protocol) {
             switch ($protocol) {
                 case 'http':
-                case 'https':   $value = preg_replace_callback('~(?:(https?)://([^\s<]+)|(www\.[^\s<]+?\.[^\s<]+))(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { if ($match[1]) $protocol = $match[1]; $link = $match[2] ?: $match[3]; return '<' . array_push($links, "<a $attr href=\"$protocol://$link\">$protocol://$link</a>") . '>'; }, $value); break;
-                case 'mail':    $value = preg_replace_callback('~([^\s<>]+?@[^\s<]+?\.[^\s<]+)(?<![\.,:])~', function ($match) use (&$links, $attr) { return '<' . array_push($links, "<a $attr href=\"mailto:{$match[1]}\">{$match[1]}</a>") . '>'; }, $value); break;
-                default:        $value = preg_replace_callback('~' . preg_quote($protocol, '~') . '://([^\s<]+?)(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { return '<' . array_push($links, "<a $attr href=\"$protocol://{$match[1]}\">$protocol://{$match[1]}</a>") . '>'; }, $value); break;
+                case 'https':   $value = preg_replace_callback('~(?:(https?)://([^\s<]+)|(www\.[^\s<]+?\.[^\s<]+))(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { if ($match[1]) $protocol = $match[1]; $link = $match[2] ?: $match[3]; return '<' . array_push($links, "<a $attr href=\"$protocol://$link\">$protocol://$link</a>") . '>'; }, $value) ?: $value;
+                    break;
+                case 'mail':    $value = preg_replace_callback('~([^\s<>]+?@[^\s<]+?\.[^\s<]+)(?<![\.,:])~', function ($match) use (&$links, $attr) { return '<' . array_push($links, "<a $attr href=\"mailto:{$match[1]}\">{$match[1]}</a>") . '>'; }, $value) ?: $value;
+                    break;
+                default:        $value = preg_replace_callback('~' . preg_quote($protocol, '~') . '://([^\s<]+?)(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { return '<' . array_push($links, "<a $attr href=\"$protocol://{$match[1]}\">$protocol://{$match[1]}</a>") . '>'; }, $value) ?: $value;
+                    break;
             }
         }
 
         // Insert all link
-        return preg_replace_callback('/<(\d+)>/', function ($match) use (&$links) { return $links[$match[1] - 1]; }, $value ?? '');
+        return preg_replace_callback('/<(\d+)>/', function ($match) use (&$links) { return $links[$match[1] - 1]; }, $value ?? '') ?: $value;
     }
 
     /**
@@ -1873,4 +1876,14 @@ class Helper
         $then = mb_substr($string, 1, null, $encoding);
         return mb_strtoupper($first_char, $encoding) . $then;
     }
+
+    /**
+     * This is needed to allow using regexes for large texts.
+     */
+    public static function setPcreBacktrackLimit()
+    {
+        if ((int)ini_get('pcre.backtrack_limit') <= 1000000) {
+            ini_set('pcre.backtrack_limit', 1000000000);
+        }
+    }
 }
diff --git a/app/Thread.php b/app/Thread.php
index 3940f16d..36811d1c 100644
--- a/app/Thread.php
+++ b/app/Thread.php
@@ -308,11 +308,12 @@ class Thread extends Model
 
         // Change "background:" to "background-color:".
         // https://github.com/freescout-helpdesk/freescout/issues/2560
-        $body = preg_replace("/(<[^<>]+style=[\"'][^\"']*)background: *([^;() ]+;)/", '$1background-color:$2', $body);
+        // Keep in mind that with large texts preg_replace() may return null.
+        $body = preg_replace("/(<[^<>]+style=[\"'][^\"']*)background: *([^;() ]+;)/", '$1background-color:$2', $body) ?: $body;
 
         // Cut out "collapse" class as it hides elements.
-        $body = preg_replace("/(<[^<>\r\n]+class=([\"'][^\"']* |[\"']))(collapse|hidden)([\"' ])/", '$1$4', $body);
-        
+        $body = preg_replace("/(<[^<>\r\n]+class=([\"'][^\"']* |[\"']))(collapse|hidden)([\"' ])/", '$1$4', $body) ?: $body;
+
         return \Helper::purifyHtml($body);
     }
 
@@ -352,7 +353,7 @@ class Thread extends Model
                 return sprintf('target="_blank" %s', array_shift($m2));
             }, $tpl);
 
-        }, $body);
+        }, $body) ?: $body;
 
         return $body;
     }
@@ -1440,4 +1441,36 @@ class Thread extends Model
     {
         return $this->type == self::TYPE_MESSAGE;
     }
+
+    public static function replaceBase64ImagesWithAttachments($body, $user_id = null)
+    {
+        \Helper::setPcreBacktrackLimit();
+
+        $body = preg_replace_callback("#(<img[^<>]+src=[\"'])data:image/([^;]+);base64,([^\"']+)([\"'])#",
+            function ($match) {
+                $attachment = null;
+                $data = base64_decode($match[3]);
+
+                if ($data) {
+                    $attachment = Attachment::create(
+                        $file_name = number_format(microtime(true), 4, '', '').'.'.$match[2],
+                        $mime_type = 'image/'.$match[2],
+                        $type = Attachment::TYPE_IMAGE,
+                        $data,
+                        $uploaded_file = null,
+                        $embedded = true,
+                        $thread_id = null,
+                        $user_id = \Auth::id()
+                    );
+                }
+                if ($attachment) {
+                    return $match[1].$attachment->url().$match[4];
+                } else {
+                    return $match[0];
+                }
+            }, $body
+        );
+
+        return $body;
+    }
 }