sql error in admin mail.php - send mail and newsletters

When I upgraded this site, I removed the newsletter subscriber plugin completely. Perhaps I removed too much. I don't know. the error message is right syntax to use near 'as s left join zen_customers as c on c.customers_id = s.customers_id' at line 1
in:
[select c.customers_firstname, c.customers_lastname, s.email_address as customers_email_address from as s left join zen_customers as c on c.customers_id = s.customers_id ]

Note that there is no longer a from the customers table in that query. I checked back thru everything I can think of. Including the queries in the query tablelwhich appear to be the same as a default install. I don't see any left over files nor do I see files that weren't replaced and upgraded.

Suggestions?

To properly remove that plugin, you need to start with the plugin's source files and use a tool such as WinMerge or Beyond Compare (my favorite) to compare against the site's file-set to fully back-out the changes that the newsletter-only subscribers mod injected. It's a bear of a task, since the plugin's changes tentacle wide and far.

You could also try installing the Debug Backtrace plugin, which will give you a backtrace of the calling modules that resulted in the error. I've found that invaluable at times, especially when errors are "created" within functions who are simply victims of invalid data being passed.