Hi!

I'm developing some custom mailing templates inheriting mass_mailing module (Odoo 14). I placed thumb images where you choose mailing template when you create a new mailing and also logo of the company in mailing. I develop this with docker image (Odoo 14) on my local environment I see the images and everything works well but, when we upload this theme to production environment and install it, I don't see any of these images. It gives very common error when I try to open the url of these images. 

Not Found
The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again. 

By the way, other then images, all the styles (css) that I defined work well.

Do you have any idea why I see the images on my local environment but I don't see them on production environment?

my custom module name:

mass_mailing_themes_custom

my code:

<template id="custom_email_designer_snippets" inherit_id="mass_mailing.email_designer_snippets" name="Custom E-mail designer snippets">
	<xpath expr="//div[@id='email_designer_themes']" position="inside">
		<div data-name="custom_template" title="Custom Mailing Template" data-img="/mass_mailing_themes_custom/static/src/img/theme_imgs/custom_thumb" data-images-info='{"logo": {"format": "png"}}'>
			<t t-call="mass_mailing_themes_custom.theme_custom_template"/>
		div>
	xpath>
template>
<template id="theme_custom_template">
	<t t-call="mass_mailing.s_mail_block_paragraph"/>
	<t t-call="mass_mailing.s_mail_block_footer_separator"/>
	​<img src="/mass_mailing_themes_custom/static/src/img/theme_custom_1/logo_grey_120x41.png"width="60"alt="Logo grey"/>
template>