Email deferred due to Greylisting

Greylisting is a spam-prevention method that some mail servers use to temporarily delay email from senders they don't recognize yet. This article is for anyone sending email through Titan Mail whose message shows a "Deferred" status because of greylisting. After reading it, you'll understand why this happens and what to check so your email is delivered.
 

Troubleshooting

Problem: An email you sent does not reach the recipient right away. Your Email Logs show the message status as Deferred, with a message similar to this:

2021-07-05 08:07:07  outgoing@example.com  Outgoing  Deferred
(host mail.example.net said: 450 4.7.1 <recipient@example.com>:
Recipient address rejected: Greylisting in action, please come back later)

Cause: The recipient's mail server uses greylisting. Greylisting temporarily rejects email from a sending server it doesn't recognize yet. If the sending server tries again, as Titan Mail automatically does, the recipient's server accepts the message and remembers the sender for next time. Most spam senders never retry after a rejection like this, so greylisting blocks a large share of spam without blocking real senders for long.

Fix:

1. Wait a few minutes. Titan Mail automatically retries a deferred message, so most emails go through on the next attempt without you doing anything.
2. Check your Email Logs again after a few minutes. You will see the message status change from Deferred to Delivered once the retry succeeds.
3. If the message is still deferred after several attempts, make sure your domain's SPF record (a DNS setting that lists which mail servers can send on your domain's behalf) includes Titan's sending IP addresses. Contact Titan Support if you need help checking this.
    

What success looks like

Your Email Logs show the message status as Delivered, and the recipient receives your email without further delay.