Best practices for sending emails and avoiding spam [closed]

Email content is just one ingredient among "best practices for sending emails".

There are many other factors that influence the classification as spam or not.

IP address reputation

First, the IP address itself. For example: if your IP is in a low reputation range, this alone can be a reason to reject the email, regardless of everything else. I've had this experience: I hired a very cheap VPS provider, and I found that any email sent from their servers are automatically rejected by Yahoo! Mail. In short: the IP address reputation is an important factor. Serious, professional and modern providers with a strong anti-spam policy will have a good reputation and this does not become a problem.

DNS records

Another important technical factor is related to DNS records. Ideally, the IP address being used for submissions must be firmly associated with the domain of the sender address, including with reverse DNS properly configured. In addition, records SPF and Sender ID, as well as signatures DKIM and DomainKeys in all sent emails, are great measures to avoid the spam box and cultivate a high reputation as a sender. With every system I prepare for an application, I do all this work involving the DNS records and the signatures mentioned, and the result is usually " Inbox ", that is, no box of spam.

Ethical use

Also very important is as your server / application will make the submissions. Bought a list with millions of emails and sent the same ad to everyone? Reputation will plummet and submissions will be classified as spam . On the other hand, if your system behaves well , sending emails only to those who legitimately interact with your system, with "double opt-in" (that is, email confirmation / verification by sending a link), and following too many rules of ethical "behavior", without improper submissions, you are cultivating an excellent reputation. Maintaining email registration is another important task: sending emails to non-existent addresses, for example, inevitably happens over time, and it is important to keep track of bounces (returns), keeping the email registration base always as clean as possible.

The number of recipients can be huge, as long as your "list" has been built over time and is "true". Send a lot of emails suddenly to a lot of addresses... is spam .

When migrating a medium or large user base from one provider to another, you need to check with the provider for the usage rules for sending emails. I've traded with more from a provider and our server has been whitelisted, for the fact that we follow the best practices in sending (in the case, sending daily spiritual messages to about 6000 addresses - all registered of their own free will, with double opt-in, etc). Providers usually have a control/filtering/limit mechanism, but that can be disabled upon request, enabling larger quantity shipping.

Technical Care

Following the guidelines above and a few more technical care in sending the messages (correct and valid Return-Path, correct and valid sender address, correct SMTP protocol dialog), becomes almost irrelevant the content of the email, if your email is really honest and appropriate... in other words: case your email Don't really be spam, so it is very difficult for it to be classified as spam due to the content. (That said, of course there are various tips that boil down to nothing more than" common sense", avoiding overly" promotional " language, or obscene words, etc.)

Reader compatibility

Your specific questions, except about quantity of recipients, which we have already seen, are about: content-type, CSS, images, and mail() x PHPMailer.

Are pertinent and important questions, but very little relevant to the score as SPAM or not. In fact, an email that is just HTML with a image, without any text, can be considered suspicious. Other than that, the answer is "whatever", considering the question of punctuation as spam.

These questions are important yes to build emails that are correctly presented in as many environments as possible: Outlook, Thuderbird, Gmail, Yahoo, and other email readers, which are many. Yes, these answers need to be sought and best practices must be followed.

The best practices of HTML for email are quite different from those for web sites. In fact, they are even opposites. And they depend a lot on what you want. For simple transactional emails, it is sometimes preferable not to use HTML, but to stick with plain text. You can also rely on the model of the big sites, such as Twitter, Facebook, Google, etc. - as far as HTML is concerned.

CSS must be inline (attribute style). In general, the use of image should be restricted to decoration, and not be the main. But it depends: if your mailing is Product Catalog, it may be important to have the images of the products.

The mail () function can be used, but libraries like PHPMailer or others make coding a lot easier and are a good option. I think the most important thing is the "behind" structure... I usually install and configure Postfix to make the submissions...

email Deliverability it is a broad and extensive topic... I hope I helped a little.