Go to the "Email Marketing" app in your Odoo instance.

In the "Configuration" menu, select "Settings".

In the "Outgoing Mail Server" section, select "Sendgrid" from the drop-down menu.

In the "Advanced" tab, select "Sendgrid" as the outgoing mail server for the "newsletter" option.

Save your changes.

Go to "Settings" -> "Technical" -> "Email" -> "Outgoing Mail Servers"

Create a new mail server and set it as the default one

Go to "Settings" -> "Technical" -> "Email" -> "Templates"

Edit the template that you want to use for non-newsletter emails and set the new outgoing mail server as the one to use

Test sending an email using the new template to ensure it's using the correct outgoing mail server.