I dont understand the issue with plugin age… if it just does a simple job that does not change over time, why would the plugin change? just to make folks feel better?
the issue ‘usually’ arises because WP send email using an address of wordpress@yourdomain… many hosts, especially shared hosting servers, block email from an address if the email address doesnt actually exist… another option could be to simply create the dummy wordpress email address on your domain…
the smtp plugins out there, really just change the address from wordpress to some other email address that you probably already use (such as admin@yourdomain.com or yourname@yourdomain.com)…
WP using the wordpress@yourdomain.com address for sending emails has been that way since the beginning, so a plugin changing that just has not had to be updated…
so afraid we cannot recommend another because we have no experience with any other one than what we recommended… but just take a look at the plugin repository and find one you like better: https://wordpress.org/plugins/tags/smtp