Function to prevent numbers (or any other string) from being automatically turned into a link inside Gmail, Outlook, etc.

function.php

<?php
function prevent_text_link( $str ) {
  
  // Get total length of string
  $strlen = strlen( $str );
  
  // Get number of middle character in string
  $middle = round( intval( $strlen ) / 2 );
  
  // Loop through each character in the string and add an empty HTML tag in the middle
  $output = '';
  for( $i = 0; $i <= $strlen; $i++ ) {
    $char = substr( $str, $i, 1 );
    if( $middle == $i ) {
      $output .= '<em></em>';
    }
    $output .= $char;
  }
  
  return $output;
}

// $string is the original string and $formatted_string is the modified one that can be used in the email
$formatted_string = prevent_text_link( $string );
?>