It is built for the size of list a normal Joomla site actually has: a few dozen to a few thousand addresses. Everything that usually breaks at that scale — PHP timeouts halfway through a send, one bad address aborting the whole run, no way to tell what went wrong — is handled.

Double opt-in. An address is stored as Pending with a 48-character random token and only becomes Confirmed when the recipient clicks the link. Nobody can add somebody else to your list.
Six ready-made e-mail layouts — simple letter, hero with a call to action, two-column roundup, product grid, event invitation, and a text-only minimal design. Preview one, insert it, edit the words.
Placeholders for name, e-mail, site name, site URL, date, and the unsubscribe link, replaced per recipient at send time.
Live preview of any template rendered with sample data, before a single message goes out.
Test send to one address, so a typo costs one e-mail instead of your whole list.
Batched sending with a progress bar. Messages go out in configurable batches, each recipient's outcome recorded individually. A timeout costs you the current batch, not the run.
Resume an interrupted send. Close the tab by accident and the job waits; a Resume button picks it up exactly where it stopped, with no duplicates.
Send history listing every newsletter with sent, failed and total counts — and for each failure, the reason your mail server gave.
One-click unsubscribe via the List-Unsubscribe header, so Gmail and Outlook show an Unsubscribe control next to your name and readers opt out instead of pressing Spam.
Throttling for hosts that cap outgoing mail per hour.
CSV export of your subscriber list, filtered exactly as you see it on screen.
Simple Newsletter uses Joomla's own mail settings, so whatever already works for your contact form works here too — PHP mail, SMTP or sendmail. The Send screen shows you the address messages will actually go out from, whether it comes from Global Configuration or from the component's own options, and warns you about the two settings that silently swallow newsletters: Joomla's Send Mail master switch being off, and a From address your SMTP account is not allowed to send from.

The extension makes no outgoing connections of any kind. No telemetry, no licence check, no remote fonts or scripts in the admin. The only traffic it generates is the e-mail you tell it to send. Subscriber data never leaves your server.