Mailspoofsent is a Bash script that sends an email using the smtp.mailfrom and header.from addresses specified by the user. It also changes some configuration values that are required to spoof email bypassing spam filters.

The tool currently delivers spoofed mails successfully to:

• Google Workspace Professional (with smart features)
• Google Workspace
• Office 365 Professional
• Outlook Personal (50%)
• Yahoo Personal (50%)
• Google Personal
• Hotmail Personal

It is recommended to read the "Explanation" section.

The install.sh script can be used to install all requirements.

• Postfix (when installing Postfix choose -> Internet Site -> Name doesn't matter)
• Mailutils
• Python3 (only for web UI)
• Python3 PIP (only for web UI)
• Flask (only for web UI)

This part is not required, but it can be helpful for bypassing spam filters.

• Public IP address -> Valid PTR record

Install on Linux:

git clone https://github.com/mverschu/mailspoofsent
cd mailspoofsent
chmod +x mailspoofsent.sh
./mailspoofsent

Usage: ./mailspoofsent.sh [--bcc bcc_address] --mail-from mail_from --mail-to mail_to --mail-envelope mail_envelope --subject subject --body body [--htmlbody body.html] --spoof-domain domain [--web]

Options:
  --bcc bcc_address   Specify a bcc address for the email
  --mail-from         The mail address shown in mail client
  --mail-to           The recipient's email address
  --mail-envelope     The under control mail address to spoof e.g. SPF
  --subject           The subject of the email
  --body              The body of the email
  --htmlbody          The HTML body of the email (provide file path)
  --spoof-domain      The domain to spoof from under control of attacker
  --web               Start the MailSpoofSent Web UI

The new version of MailSpoofSent offers users to use a Web UI. This is currently under development to be improved.

The mail-from address is the address that appears in the "From" field of the email and is the address that the recipient sees as the sender of the email. The mail-envelope address, on the other hand, is the address that is used as the actual sender of the email and is used by the mail server to route the email.

For example, if the mail-from address is [email protected] and the mail-envelope address is [email protected], the recipient of the email will see that the email was sent from [email protected], but the mail server will use [email protected] to route the email.

In some cases, the mail-from and mail-envelope addresses may be the same, but it is also common to use a different address for the mail-envelope to protect the identity of the real sender or to prevent the email from being marked as spam.

DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email authentication protocol that is used to determine whether an email is likely to be legitimate or not. One of the checks that DMARC performs is to compare the mail-from and mail-envelope addresses in the email to see if they match.

If the mail-from and mail-envelope addresses match, it is a strong indication that the email is legitimate and not a spoofed email. However, if the addresses do not match, it may be an indication that the email is a spoofed email and should be treated with caution.

In order to perform this check, DMARC uses the DKIM (DomainKeys Identified Mail) and SPF (Sender Policy Framework) authentication methods to verify the authenticity of the email. If both of these authentication methods pass, DMARC will then compare the mail-from and mail-envelope addresses to determine if the email is likely to be legitimate.

Overall, the comparison of the mail-from and mail-envelope addresses is an important part of the DMARC email authentication process and helps to protect against spoofed emails.

SPF (Sender Policy Framework) is an email authentication method that is used to verify the identity of the sender of an email. SPF works by allowing the owner of a domain to specify which IP addresses are authorized to send email on behalf of that domain.

When an email is received, the receiving mail server can use the SPF record of the domain in the mail-envelope address to verify that the IP address of the sending server is authorized to send email for that domain. If the IP address is not authorized, the email may be flagged as spam or rejected.

However, it is important to note that SPF only checks the domain in the mail-envelope address, not the mail-from address. This means that an attacker could potentially bypass SPF checks by setting the mail-from address to a different domain than the mail-envelope address.

For example, if the mail-envelope address is [email protected] and the SPF record for the example.com domain only allows emails to be sent from a specific set of IP addresses, an attacker could set the mail-from address to [email protected] and still send an email that would pass the SPF check.

In order to prevent this type of attack, it is recommended to use additional email authentication methods, such as DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting and Conformance), which can provide more robust protection against spoofed emails.

DKIM (DomainKeys Identified Mail) and SPF (Sender Policy Framework) are two email authentication methods that are often used together with DMARC (Domain-based Message Authentication, Reporting and Conformance) to protect against spoofed emails.

DKIM works by adding a digital signature to the headers of an email, which can be used to verify the authenticity of the email. The digital signature is created using a private key that is held by the domain owner, and the corresponding public key is published in the domain's DNS records.

When an email is received, the receiving mail server can use the public key to verify the DKIM signature and determine if the email is likely to be legitimate. If the DKIM signature is valid, it indicates that the email has not been modified in transit and is likely to be legitimate.

The sending Mail Server IP (Received From IP) must match the IP of the domain in the Pointer (PTR) record, also known as the Reverse DNS record. The PTR record verifies that the sending domain is associated with that sending Mail Server IP.

A PTR record should be set to match the domain given in the '--spoof-domain' argument.

Email Service Providers like Gmail, Yahoo, etc. may block emails coming from a mail server that does not have Reverse DNS in place.