Send emails through cloudflare worker from Mail App like Thunderbird.
Is there a way I can send an email through a cloudflare worker from Thunderbird or other Mail Clients?
HYou could probably implement JMAP via a Worker, but Thunderbird itself doesn't support JMAP yet. Note too that you would have to find a provider to actually send the emails, so you might as well just use them directly, rather than try to run it through a Worker...
AWhy do I need a provider to send the emails? 
HBecause Cloudflare itself doesn't provide email sending support. You can receive emails to verified email addresses with #email-routing, and you can send to said verified emails, but to be able to send emails to any email address, you need an external provider.
Di use resend.com but any http based email service will work including mailchannel integration with cloudflare
