Email is an important channel of communication with the user, and for many services (for example, for couponers) work via email becomes the basis of the business model. At the same time, as active users, we are greatly annoyed when the mailbox begins to flood with mailings, information letters, invitations from strange services, i.e. the fact that in everyday life we ​​simply call “spam”. The realities of our life are such that spam makes up 80-90% of the incoming stream of emails to any mail server. Therefore, for modern mail service, spam filtering is a must have.

Exact filtering algorithms are usually hidden for obvious reasons. However, we are ready to lift the veil of secrecy over one of the aspects of Mail.Ru's anti-spam system to help colleagues from different Internet companies to efficiently and effectively produce email-mailing for our general users. In fact, this is a set of recommendations on how not to go to spam and increase the percentage of letters delivered to the final recipient. I hope many of them will be useful.

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Evaluation of reputation, or "Take care of the honor of his youth"

“If you don’t receive letters from me, don’t think that I don’t write them”
Jonathan Safran Foer

Modern filtering systems are rather successfully fighting the so-called “black spam” - mass mailings, for the implementation of which hacked servers and botnets are used. Even if such a newsletter bypasses spam filtering, when the first complaints are received, the system adapts and changes necessary for blocking are made to the filters.

However, the analysis of user complaints shows that at the moment the biggest problem is the distribution, carried out by quite legal email-marketing services or large companies. 70% of user complaints (clicks of the “this is spam” button) are complaints about letters from completely legal services, often known in the market, having an official legal entity, a beautiful office, and a vigorous and efficient marketing department. Of course, this is 70% of the complaints about the letters, which still appeared in the mailboxes after the filters work, but the figure, you must agree, is impressive.

Obviously, the email provider’s anti-spam system cannot remain indifferent to 70% of the complaints signals from its customers, therefore, the situation when another victim of effective email marketing becomes a regular occurrence of a “soulless machine”.

We want the criteria on the basis of which we make decisions to be as clear as possible. After all, in the end, the goals of the mailbox provider and the "legal" mailer are the same: the mailing should be received by those who are interested in it, and the response to it should be as positive as possible. Tactics "carpet spamming" can be beneficial only to the criminal business and one-day firms.

Our anti-spam system consists of several levels of spam filtering. In particular, a reputational approach is in place to assess the integrity of large mailers, which includes many criteria. The main ones are:
- the number of non-existent addresses in the list;
- the level of user complaints (clicking on the "Spam" button in the mail web interface),
- the number of addresses of trap addresses (specially instituted and “illuminated” somewhere addresses intended for spam trapping),
- the proportion of letters deleted without reading.

When evaluating the type of distribution is taken into account. For example, notifications about the actions of friends in social networks or some types of transactional letters are often deleted without reading, for them the weight of the corresponding criterion will be small.

Well, now the most important thing: the initiators of mailings can and should influence each of these criteria.

Why did I get it?

“Anonymous letters are good because they do not need to be answered”
Alexander Dumas son

It is this question most often leads to pressing the "Spam" button. User registration and subscription user must be obvious and obvious to him. It should not be possible to add unverified addresses to the distribution database. To achieve this is quite simple.

Right:
In case of registration, double confirmation (Double opt-in) of the e-mail box is used. That is, a letter is sent to the user with a unique link to complete the registration (“To complete registration, click the link ...”).

If a user logs in via the Mail.Ru API or using another external social network or service (or using a unique link from the invitation letter), providing an already validated email address, then the Confirmed opt-in mechanism is used, i.e. during registration, the user must receive a letter of notification (“Congratulations on your successful registration ...”).

The letter contains information about exactly how the user has given his consent to the newsletter, especially if it was sent after some time, for example, “Thank you for registering in the regular customer program” and information about the reply.

Wrong:
The user does not realize that he is registering on the service and accepts the terms of the user agreement. For example, he thinks that he just logged into the service with a Mail.Ru account.

The default checkbox is “subscribe to newsletters”.

Confirmation letters already have ads. Since such letters are sent before the completion of the registration process and may contain third-party addresses (users often make mistakes or intentionally enter “left” addresses such as anna@mail.ru), the consent to receive advertising information from the user cannot yet be considered received.

There is a common misconception that it is impossible to apply the double opt-in mechanism to addresses obtained offline (via profiles in stores, etc.). But, as practice shows, when transferring the subscriber base from paper to electronic form, errors are extremely frequent. Therefore, nothing interferes in exactly the same way first by sending a confirmation letter to the user. And only in the case of passing the link add the address to the database of subscribers.

Consent to the newsletter is not all

Even obtaining the prior consent of the user does not guarantee that he will not perceive the letter as spam. To prevent this from happening, both the business and the distribution services need to remember the following rules that help the user recognize the letter with really useful information and not send it immediately to spam.

An invitation or a reminder to complete the registration must be sent no later than two to three months after the invitation is initiated or the registration begins.

Reminders should arrive no more than once every two weeks.

An invitation letter to one user is recommended to send no more than 1-2 times.

In any letter, its type must be indicated, especially in the case of invitation letters. The invitation “Your friend Ivan Ivanov invites you to the site example.com” will be more friendly perceived by the user than “You have written a letter!”. Even if in the second case, the user reads the letter, he is more likely to return to the box and mark the letter as spam if he was not interested in the invitation.

In the case of sending invitations to the address book, invitations should be limited and sent only to those whom the user chooses. In addition, letters must contain sufficiently complete information about the inviting party.

A protection mechanism should be implemented against the automatic sending of letters and cheating, especially if the user receives bonuses for inviting friends. Please note that cheating is possible even when contacts are taken only from the address book - the user can import arbitrary contacts into the book.

Unsubscribe

"This is my first of all the last letters to you ..."
Janusz Leon Vishnevsky

Any letter sent to the user should contain information about the reply. This information should be visible and easy to read, because if the user wants to unsubscribe and does not see how to do it, he will press the "Spam" button.

For the same reason, the process of unsubscribing itself should be simple and done in 1-2 clicks, not more. The user should not be required to perform any complex actions, such as entering or recovering a password, filling out forms, etc. Filling out the questionnaire can be added as an optional step after the end of the formal reply.

When using the List-Unsubscribe service header, which allows you to instantly unsubscribe, the unsubscribe process should be completed immediately after going to the URL specified in it or receiving a letter to the address indicated in it. In this case, the user should not be required additional actions, because usually this process is performed automatically and the result is not visible to the user.

Takeovers, mergers, renames

When acquiring startups and merging companies, it is useful to notify users about this, then sending from a new domain will not cause surprise or suspicion.

Well, if you save your account settings. For example, the user was registered on the service, but unsubscribed from receiving letters (unchecked in the settings). It is logical to assume how he will respond to an unexpected resumption of distribution. The same applies to the settings for the frequency of receiving newsletters.

Postmaster Mail.Ru

“The letters of an intelligent person reflect the character of those to whom they are addressed.”
Georg Christoph Lichtenberg

So how can you keep track of your reputation? For domain owners, we have the Postmaster Mail.Ru service - we have already talked about it on Habré (for example, one , two ). It was created specifically for mail senders who want to improve not only the deliverability, but also the quality of their mailings.

To start using Postmaster Mail.Ru, you need to add your domain and confirm the rights to it. Emails must be authenticated using Domain Keys Identified Mail (DKIM) technology. This mechanism will help ensure a consistent reputation within your domain. The presence of a Sender Policy Framework (SPF) record for the protocol for sending email via SMTP does not affect the viewing of statistics. But we will remind about its absence, because SPF is used, for example, when displaying the service icon in the list of letters.

Using statistics, you can monitor the reputation and key parameters that affect it.

Also, by registering with Postmaster, each sender can configure the FBL to receive reports to their chosen mailing address. FBL is an industry standard supported by major mailbox providers such as AOL, Yahoo, and Microsoft (Hotmail and Outlook.com). The report is generated when the user clicks the “This is spam!” Button.

This information is invaluable for the e-mail sender because it allows you to unsubscribe the user in a timely manner, increasing the reputation and, as a result, the deliverability of letters. Mailbox providers require responsible data. Receiving FBL reports should not initiate any further contacts with users (neither telephone, nor written, nor others). On the contrary, it should lead to the immediate and unconditional unsubscribe of the user.

To be continued ...

The following posts will discuss technical recommendations and tools to influence letter deliverability and reputation. If you are interested in certain aspects, unsubscribe in the comments - answer the questions or try to touch them in the next post.