Hi,
As you have found out you can't change this in Acymailing. All major mass mailing solutions offer an online view like Acymailing does.
The only thing you can try is to add a rewrite rule to your .htaccess that will remove the "tmpl=component" string from your url.
Please note that this may cause css conflicts between your email and your website template.
You can try the code below. Please backup your .htaccess file before you make any changes.
RewriteEngine On
RewriteCond %{QUERY_STRING} (^|&)tmpl=raw(&|$)
RewriteCond %{QUERY_STRING} !(^|&)userid=([^&]+)(&|$)
RewriteRule ^ %{REQUEST_URI}?%{QUERY_STRING_PARAM} [QSD,L]
