It sounds like you have set up your digital products correctly and have tested your SMTP server using normal emails, but you are experiencing issues with sending emails with attachments.
Here are a few things you can check:
Check the attachments: Make sure that the attachments you have specified for the digital products are in the correct format and are accessible. Also check that the attachments are not too large to be sent by email.
Check the email templates: Make sure that the email templates for the digital products are set up correctly and include the attachments.
Check the email settings: Make sure that the email settings in your Odoo configuration are correct, including the SMTP server, port, and login credentials.
Check the log files: Check the log files of your Odoo server and SMTP server for any error messages related to sending the emails.
Check the restrictions of your SMTP server: Some SMTP servers may have restrictions on the types of files that can be sent. Also, check the size of the attachments, some SMTP servers may have a limit on the size of attachments that can be sent.
Check in your email client: Verify that the emails are not sent to the spam folder, or blocked by your email client.
Check your security rules: Make sure that your security rules in your firewall or network configurations are not blocking the email traffic.
If after checking all of the above and the problem persist, you may consider to try with another SMTP service like Amazon SES, Mailgun, Sendgrid, etc.
It's also worth noting that the email sending process can be a bit tricky and may require some troubleshooting. If you continue to have issues, you may want to consider consulting with an expert or the Odoo community for further assistance.
I have same question, digital products is enabled, sellable item (set as consumable) have attached files, but no files sent after payment confirmation.