What to do if you're added to a spam blacklist

Andronautic does not send emails through its own servers. Instead, it uses an existing, dedicated email account reserved for that purpose, acting like an email client such as Mozilla Thunderbird, Microsoft Outlook, or Apple Mail.

If your email server’s IP address or your domain name gets flagged and added to a blacklist, you will need to contact the organization behind that list to have it removed. All major blacklist providers publish information on their websites about how to get removed from their lists.

Example of a Spamhaus error message:

550 5.7.1 Service unavailable, Client host [x.y.z.t] blocked using Spamhaus. To request removal from this list see https://www.spamhaus.org/query/ip/x.yy.z.t

Example of a Barracuda error message:

Remote Server returned '550 permanent failure for one or more recipients (someuser@example.com:blocked)'

How Andronautic handles email

Andronautic uses a specific email address to send and receive messages related to bookings, for example, bookings@ejemplo.com. To set this up, there is a tab called “Email Credentials” on your profile page in the backoffice, where you can configure your email account in a way similar to any other email client.

Every few minutes, Andronautic connects to the email server to check for new messages using the incoming mail credentials. New emails are stored in the database and then linked to an existing booking or request whenever possible. These messages are then displayed within each booking, helping agents be more productive when managing bookings.

When sending a message to a client through the booking system, Andronautic uses the outgoing mail credentials to send the email to the specified address, also storing a copy of it in its database.

This simplifies things, since no additional configuration is needed on either our servers or the client’s (as long as they are already properly configured).

About blacklists

An email blacklist is a database that helps determine which emails should be considered spam. Essentially, it is a filter that can determine whether an email reaches its intended recipient’s inbox or not. It is used by organizations such as internet service providers, email service providers, and antispam providers to prevent spam from reaching their systems. Blacklists can be based on IPs or on domains.

They work as follows: when you send an email (sender) and it is received by an email service provider (recipient), the provider decides whether the email looks legitimate by checking the originating IP address and domain name against one or more blacklists. The email then passes through the provider’s internal spam filters to check for anything that is not allowed (for example, attachments using the .zip extension), and if the email passes these checks, it is delivered to the recipient’s inbox.

Very large email service providers have their own internal blacklists, but many also use public lists managed by companies that specialize in this field. Some of the most widely used are:

• Spamhaus. Manages numerous lists used by email and internet service providers around the world.
• Barracuda. Its list is made up mainly of addresses that send spam to its system.
• Spamcop. Uses spam trap addresses and spam reports to build its lists. It also applies a points system based on spam complaints before adding any address.
• Invalument. Uses a combination of 3 blacklists that it manages itself. Like Spamhaus, each list tracks different information, including IP addresses and domain names.

Since the lists these companies manage are used by email providers and large companies worldwide, you need to make sure your IP address is not on them, or your email deliverability will be seriously affected.

Reasons you might get labeled as a spammer

When an IP address is known for sending spam, it appears on DNS blocklists (DNSBL). These blocklists protect email users from opening potentially harmful spam sent from IP addresses that show suspicious activity.

There are three main reasons why your email server’s IP address or domain name might end up on a blocklist:

• Poorly designed marketing campaigns.
• Poor configuration of your domain’s email server or DNS zone.
• Viruses or malware.

Marketing campaigns that include spam trap addresses

By their very nature, spammers use huge lists of email addresses, many of them scraped from websites. For example, the ventas@empresa.com link on your website is probably in dozens of spam databases. Addresses are also bought and sold on a black market.

Antispam companies and blocklist operators keep their own special email addresses, known as “spam traps,” secret. Antispammers deliberately advertise their trap addresses (for example, on websites) so that spammers pick them up into their address books.

For this reason, you should never buy an email list when designing and running an email marketing campaign. The addresses are, at best, outdated and, at worst, spam trap addresses.

Misconfigured DNS zone or email server

Since the year 2000, spam has gradually become a serious problem for the internet. Today, it is estimated that around 85% of daily email worldwide is marked as spam. Because of this, a series of technical measures have been implemented over the years. These are, or should be, included as part of the paid service from a mail or internet service provider, or applied by system administrators in larger companies.

Unfortunately, given the complexity of some of these measures, they are often applied incorrectly or only partially. You can check these configuration values using online tools such as The MX Toolbox or Experte, and then contact your mail or internet service provider. The most important thing to check is the Sender Policy Framework (SPF) record in your domain’s DNS zone.

Viruses and malware

Both at home (remote work) and in the office, it is common practice to use a local network (whether wired or Wi-Fi) with a shared internet access point (i.e., a router) for all devices connected to it, meaning a single public IP address for all of them.

Any of the computers, mobile phones, or similar devices on such a local network can be infected with viruses or malware. You may not know it, but it will affect your active email and cause you to appear on spam blacklists.