Plugin not using SMTP Mailer

The only way I can send email from my WordPress installation is using SMTP mailer, which was fiddly to set up. WP-DB-Backup doesn’t appear to use this and emailed or scheduled backups fail to be sent.

I see related topics. There is a suggestion to sign-up to Mailjet. OK, but how do I integrate that with the plugin, I have no desire to reroute my existing mail, which works, through a different service.

Thanks