Email deliverability questions

Almost always because the domain’s email authentication is incomplete. Publish SPF, DKIM and DMARC records for your domain and delivery improves markedly — Gmail and Outlook now expect all three from anyone sending regularly.

An SPF record is a line in your DNS listing which servers are allowed to send email using your domain. Receiving mail servers check it, and a message from a server not on the list looks like forgery.

DKIM adds a cryptographic signature to every message you send, which the receiving server checks against a public key published in your DNS. It proves the message really came from your domain and wasn’t altered on the way.

DMARC ties SPF and DKIM together: it tells receiving servers what to do when a message claiming to be from your domain fails those checks, and where to send reports. Start with a monitoring-only policy, read the reports, then tighten it.

Use a public blocklist checker against your domain and your sending IP address. Being listed usually follows a compromised account or a form being abused to send spam — fix the cause first, because delisting without it just gets you relisted.

Authenticated mail. Both expect SPF and DKIM to pass, a DMARC record to exist, and an easy way to unsubscribe from bulk messages. Mail failing those checks is increasingly rejected rather than just filtered.

Yes, but send it through a real mailbox using SMTP rather than through PHP’s built-in mail function. Mail sent the built-in way is frequently discarded without warning, which is why form submissions seem to vanish.

Reverse DNS maps a sending IP address back to a hostname, and receiving mail servers check it. On shared hosting it is set at server level by the host, so there is nothing for you to configure.