WP E-mails sending via SMTP2Go
SMTP server: mail.smtp2go.com
SMTP port: 2525 (or 80, 25, 8025 or 587 if that doesnโt work).
Username / Password: Turn on SMTP authentication and enter your accountโs SMTP username and SMTP password.
Note: TLS/SSL is optional. TLS is available on the same ports. SSL is available on ports 465, 8465, and 443.
https://www.smtp2go.com/setupguide/official-wordpress-plugin-setup-guide
WP E-mails sending via MailerSend
If not using SMTP2GO then use MailerSend
https://www.mailersend.com/
E-mail Marketing
Use MailerLite for e-mail marketing
https://www.mailerlite.com/