Hi Sylvain,
Thanks for your advice, i've fixed the "Originator Email" field maxlength by setting it to 85.
Thus, there is a problem with lines between 205-208 at /include/trackers_run/admin/field_usage.php (it's the real file, the /support/admin/field_usage.php one is a wrapper) that don't make me sure to edit them.

===code to be fixed===
# Do not let the user change these field settings but put them in the
# form to preserve the existing setting or use the default values
# imposed at the system level
$addm_html = '<input type="hidden" name="show_on_add_members" '.
'value="'.(trackers_data_is_showed_on_add_members($field)? 1:0).'">'.
(trackers_data_is_showed_on_add_members($field)? ': '._("Always"):': '._("Never"));
$add_html = '<input type="hidden" name="show_on_add" '.
'value="'.(trackers_data_is_showed_on_add($field)? 1:0).'">'.
(trackers_data_is_showed_on_add($field)? ': '._("Always").'':': '._("Never").'');

# for these cases use the add_html value for the add_nologin_html
# field
$add_nologin_html=$add_html;
}

echo '<p><b>'._("Display this field...").'</b><ul>';
echo '<li>'._("On the submission form used by project members").$addm_html.'</li>';
echo '<li>'._("On the submission form used by other logged in users").$add_html.'</li>';
echo '<li>'._("On the submission form used by non logged in users").$add_html.'</li>';

echo '</ul></p>
<p>
<input type="submit" name="submit" value="'._("Submit").'">
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<input type="submit" name="reset" value="'
._("RESET TO DEFAULTS").'"></p>
</form>';
=== ends code to be fixed ===

In /support/admin/field_usage.php

Display this field...
# On the submission form used by other logged in users
and
# On the submission form used by non logged in users

have the same HTML name. As a result, it is impossible to change one without modifying the other all the same.

Incidentally, the default length of field "Originator Email" is 40, which is not enough.