WordPress sends mail through PHP's mail() by default, and Gmail, Outlook and most inboxes treat that mail as suspect: password resets, order confirmations and contact-form messages arrive late, land in spam, or never arrive. The fix is to send through a real mailbox instead, and the usual way to do that with Gmail means creating a Google Cloud project, an OAuth client and a consent screen, then pasting IDs and secrets into WordPress.
Postkeep does the connecting for you. Install the plugin, press Connect, sign in to the All in One WP Settings portal with a free account, and allow Gmail to send on your site's behalf. The portal keeps the connection; the plugin sends your site's mail through the Gmail API with a send-only permission - it cannot read your inbox - and the content of your messages goes from your site to Google without passing through us.
Free means free: one WordPress site per account, Gmail, no time limit, no card. The paid suite, All in One WP Settings, adds Outlook, more sites, updates from the portal, support and the rest of the suite's modules; the free plugin stays free whether or not you ever buy it.