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Kamil Porembiński
Kamil Porembiński

Why am I late in the mail?

E-mail is probably one of the most popular communication media of today. Despite the large number of instant messengers or other ways of exchanging e‑mail information, it still reigns. With its help we receive invoices, send notifications from systems or conduct project arrangements. However, when the mail arrives late, we start to pledge whether there are any failures somewhere.

A little bit of history and theory

Email was invented in 1965, and its first implementations only allowed messages to be exchanged between users of the same computer. Only in 1971, there was a possibility to communicate with users on different servers. It was then that the @ character was created, separating the user name from the address of the server on which it was located.

The protocols known to us today for sending mail – SMTP and receiving messages – POP, were created in 1982 and 1984, respectively. These are quite old protocols, which are used to exchange information between users, and despite many corrections and updates, they still fail.

Classic e‑mail flow through various systems.
Classic e‑mail flow through various systems.

How is a notification e‑mail sent, for example, by WordPress? For example, when we start the password reset procedure for the user, the CMS will generate an e‑mail message. It will be sent to the mail server, which will prepare the e‑mail and send it to the recipient via the Internet.

However, before the message reaches your inbox, it will pass through a number of filters and validation checks to eliminate SPAM.

Mail sent at 12:07 arrived at 12:27!

How does it happen that in the era of fast electronic communication, e‑mails arrive late? There can be many reasons for this and very often it is not a server failure but the specification of the e‑mail itself.

Why do messages arrive late? After all, this is electronic, it should be delivered immediately.

Anxious customer

Before we pass judgment on the servers, let’s see the most common reasons that cause delays in email delivery.

Fifty faces of the Greylist

One of the methods of defending against spammers is greylisting. Mail servers using this method have an impact on delaying mail delivery. So how does Greylisting work?

A mail server that receives an email for the first time from an unknown sender rejects the email, informing the sender of a temporary problem with receiving the email. The sender’s server, if configured correctly, will re-deliver the message after a certain period of time according to the postal protocol specification. This time the recipient’s server will accept the message.

Usually, messages from spammers are not sent again because their servers work temporarily in order to prevent their identification.

Greylisting also changes the order in which messages are delivered. Sometimes it happens that the recipient receives messages in a different order than they were sent to him. This is because the first message from the sender was rejected (grey list mechanisms), the next one was considered to be a resume and delivered correctly. After some time the first message will also be delivered.

Mail forwarding

One of the reasons why mail arrives late is the forwarding of e‑mails. Very often, having a postal address, e.g. sales@example.pl, we redirect mail to a private address such as jacek_sprzedawca@wp.pl. This type of forwarding usually works. The problem occurs when there is a lot of messages to redirect.

Imagine that the original postal address sales@example.pl is starting to receive a lot of messages. These are notifications from auction services, inquiries from customers, notifications from price comparison engines and so on. All these messages flow to the server example.pl, which will redirect them to the address jacek_sprzedawca@wp.pl.

From the point of view of the wp.pl server, the example.pl server begins to send a huge number of messages. The target server may consider this type of mailing simply as SPAM. E‑mail service providers very often introduce limits of received mail from one IP address or domain (e.g. 100 e‑mails per hour).

In this case, the target server blocks the receipt of forwarded messages or temporarily does not receive them. The redirection server will try to send a message from time to time, so the message may arrive late.

But I only redirected one message, and it still arrived late.

Tomasz B.

This type of situation most often occurs on shared servers or hostings. On a single machine there are many customers who could also set up mail redirections to the same provider.

Receiving Gmail

One of the most interesting features of Gmail is the ability to download messages from other mail servers. Thanks to this, in one place we have mail from other email addresses. This type of solution is definitely better than mail forwarding. Gmail simply logs in for us to our mailboxes and retrieves messages to each other.

Settings for downloading mail via Gmail.
Settings for downloading mail via Gmail.

If Gmail downloads mail, where do the delays come from? Mail is downloaded once in a while (every few minutes), so even though it is already on the server, it is not yet on Gmail. You have to wait until Google downloads it and shows it in its interface. You can easily check it by logging into the mail server before Gmail downloads the message.

In the Gmail panel, you can also check when you last downloaded mail. There is also the option to download messages now.