Customer Emails That Arrive Half an Hour Late

Sent at nine, received at half past

A caterer's new customer phones at ten to ask why nobody has confirmed the order change she emailed at nine. The office finds the message: it arrived at 9:31.

She is sure she sent it on time, and the message itself agrees. Mail from regular customers arrives within seconds, so the office suspects her email provider.

Her provider sent it at once. The half hour was spent at the door of the caterer's own mail server, which turned the message away on its first attempt.

Reading the times in the message

Every email carries a record of its trip, normally hidden. Most mail programs show it under an option such as view source, show original or message properties.

The date line shows when the sender pressed send. Each server that handled the message also adds a line, headed Received, with its own time.

Find the line your own server added, usually the top one, and compare its time with the line just beneath it. A half-hour gap between them means the message spent that time waiting to get into your server.

What greylisting does

Many hosts protect mailboxes with a method called greylisting. When a message arrives from a sender, recipient and sending server not seen together before, the server refuses it for now.

The refusal is temporary and polite: try again later. A properly run mail server keeps the message in its queue and tries again on its own schedule, anywhere from minutes to an hour or more.

The second attempt is accepted and the combination remembered, so later mail from the same sender arrives at once. Much junk mail software never tries twice, and its messages simply disappear.

When the sending server is properly run, nothing is lost. The sender sees no error, and the message arrives intact, only late.

Who waits longest

Greylisting delays some senders far more than others:

• First-time senders, such as new customers and new staff at a supplier.
• Large email providers that may retry from a different server, which looks like a new sender and restarts the wait.
• Servers that wait long between attempts, sometimes an hour or more.
• Order and booking systems that send notices through their own servers, some of which never retry.
• Password resets and confirmation codes that expire before they arrive.
• Regular senders after a long gap, since remembered combinations expire after some weeks.

The second explains why delays seem random. A customer on a large provider may wait an hour one day and seconds the next, depending on which of its servers happens to send.

Why hosts use it

Greylisting costs a host almost nothing and stops a great deal of junk before it reaches the slower filters. Regular correspondents are rarely delayed after their first message.

It is sometimes switched on by default on shared mail servers and seldom mentioned to customers, so a business can run on it for years without knowing.

The trade-off is a delay the business never sees, borne by the people writing to it for the first time.

Asking the host for exemptions

The host can usually exempt particular senders: a customer's domain, a supplier, the online ordering system, the bank, or the servers of large email providers.

It can also switch greylisting off for one address, such as the orders mailbox, while leaving it on for the others.

Send the host the full headers of two or three delayed messages. They show exactly which servers were refused, and save a round of guessing.

Once the change is made, send a test from an address the server has never seen, and time it.

A worked example

A tortilla maker in an industrial unit in Nanaimo makes corn and flour tortillas for restaurants and grocers from Duncan to Campbell River, with orders by email for delivery the next morning.

Orders close at 2 p.m. Twice in a month, an order sent before two arrived after it, and a restaurant ran short of tortillas the next day.

The headers showed the same pattern each time: sent at 1:50, refused by the tortilla maker's mail server, accepted on the second attempt at 2:20.

The host exempted the orders mailbox from greylisting and kept it on the other addresses. Several restaurants order from purchasing software, and its servers were added to the list of known senders as well.

The order page now says that changes after two should be phoned in, and every order receives an automatic reply, so customers can see it arrived.

What still guards the mailbox

Turning greylisting off for one address does not leave it unprotected. Checks on the sender's reputation, its permitted servers and the message content still run.

Expect a little more junk in that mailbox, and ask the host to tighten its other filters if it becomes a nuisance.

Urgent changes need a second route

Email is not instant even without greylisting. Servers can be busy, messages can be filtered, and a person may simply not be at the desk.

For anything that cannot wait, give customers a phone number and a cut-off time, and send an automatic reply so they know their message landed. Say both on the order page and in the reply itself.

The counter-case

For a business where email is rarely urgent, a half-hour wait on a first message does no harm. Greylisting keeps junk down at little cost, and leaving it on is sensible.

Some delays are not greylisting at all. The headers may show the gap at the sender's end, in a busy provider's queue, which no host setting can change.

But where orders, bookings or codes arrive by email against the clock, the host should know which addresses matter, and set them up accordingly.

Finding the half hour

1. Open the headers of a delayed message.
2. Compare the last two times to find the gap.
3. Ask the host whether greylisting is on.
4. List the senders that cannot wait.
5. Request exemptions for those senders or addresses.
6. Add an automatic reply to the orders mailbox.
7. Give a phone route for urgent changes.

Step two settles the argument. Once the headers show where the half hour went, the host, the customer and the office are talking about the same delay.

Emails from the website signed WordPress covers the mail a site sends on its own behalf, which receiving servers can doubt for other reasons.

Frequently asked questions

West Coast Media Solutions Inc. provides web design, web development, hosting, digital marketing, and business consulting to organisations across Canada, drawing on more than twenty-five years in the field.