Understanding And Managing The 'mailed-by' Tag

What is the 'mailed-by' tag? The 'mailed-by' tag is a sender identification field in email headers that helps authenticate email origins and combat spam. Who uses it? Email service providers (ESPs) and companies sending bulk emails use it. Why is it important? It builds trust, improves deliverability, and helps recipients identify legitimate senders. How is it managed? It's typically set by the ESP or through domain authentication like SPF and DKIM.

Key Takeaways

• The 'mailed-by' tag appears in email headers to identify the sending server.
• It's crucial for email authentication, spam prevention, and sender reputation.
• It's usually managed automatically by your Email Service Provider (ESP).
• Proper domain authentication (SPF, DKIM, DMARC) is essential for controlling this tag.
• Directly changing the 'mailed-by' tag is not possible; it's tied to your sending domain and ESP configuration.

Introduction

In the constant battle against spam and phishing, email providers employ various methods to verify the legitimacy of incoming messages. One such method involves inspecting the email's header information, where you might find a field labeled 'mailed-by'. This tag serves as a digital fingerprint, indicating which server or service sent the email on behalf of a particular domain. Understanding what 'mailed-by' means and how it functions is vital for anyone involved in email marketing, business communication, or simply wanting to ensure their emails reach their intended recipients without being flagged as spam. This article will delve into the intricacies of the 'mailed-by' tag, explaining its purpose, how it's determined, and what steps you can take to ensure it accurately reflects your legitimate sending practices.

What is the 'mailed-by' Tag and Why Does It Matter?

The 'mailed-by' tag is a header field found within the technical data of an email. It essentially tells you the domain name of the mail server that was used to send the email. For example, if you receive an email from your bank, and the header shows 'mailed-by: bankname.com', it indicates that the email originated from a server associated with bankname.com. This is distinct from the 'From' address, which is what the recipient sees. The 'From' address might be 'customer.service@yourbank.com', but the 'mailed-by' reveals the underlying infrastructure.

The primary purpose of the 'mailed-by' tag is to enhance email authentication and security. By specifying the sending server's domain, it provides an additional layer of verification. Email providers use this information, in conjunction with other authentication protocols like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance), to determine if an email is genuinely from the purported sender or if it's an imposter trying to deceive recipients. This helps in several critical ways: — Big Bear, CA Zip Codes: Find Any Address

• Spam Prevention: Legitimate emails with correct 'mailed-by' tags are less likely to be marked as spam. Conversely, spoofed emails often have mismatched or absent 'mailed-by' information, flagging them for scrutiny.
• Sender Reputation: Consistent and accurate 'mailed-by' information contributes positively to a sender's reputation. A good reputation means better email deliverability.
• Recipient Trust: When recipients see that an email is 'mailed-by' a domain they recognize and trust, it increases their confidence in the message's authenticity.
• Brand Protection: It helps prevent malicious actors from impersonating your domain, protecting your brand's integrity and your customers from phishing attempts.

While you can't directly 'change' the 'mailed-by' tag like editing a document, understanding its origin and how it's generated is key to managing it effectively. It's intrinsically linked to how your emails are sent and authenticated. — Hillsboro, Oregon Zip Codes: Your Complete Guide

How the 'mailed-by' Tag is Determined

The 'mailed-by' tag isn't set manually by the sender for each email. Instead, it's automatically populated based on the domain name of the mail transfer agent (MTA) or the mail service provider (ESP) that handles the actual sending of the email. Here’s a breakdown of the process: — Gilroy, CA Zip Codes: Your Definitive Guide

1. Email Sending Infrastructure: When you send an email, it doesn't usually go directly from your personal computer or a simple web server. Instead, it's processed by an MTA. For businesses and bulk senders, this is almost always an ESP like Mailchimp, SendGrid, Amazon SES, Constant Contact, etc.
2. Server Domain: The MTA has its own domain name associated with its sending servers. For instance, emails sent via SendGrid might show 'mailed-by: sg.mydomain.com' or 'mailed-by: mydomain.com', depending on configuration. Emails sent via Gmail might show 'mailed-by: gmail.com'.
3. Authentication Protocols: The presence and accuracy of the 'mailed-by' tag are heavily reliant on the correct implementation of email authentication protocols:
   • SPF (Sender Policy Framework): This is a DNS record that specifies which mail servers are authorized to send email on behalf of your domain. When an receiving server gets an email, it checks the 'mailed-by' domain against its SPF record. If the sending server's IP address is listed in the SPF record for that domain, the SPF check passes.
   • DKIM (DomainKeys Identified Mail): This adds a digital signature to the email's header, which is verified using a public key published in your domain's DNS records. DKIM helps confirm that the message content hasn't been tampered with and that it originated from an authorized domain. The 'DKIM-Signature' header often includes the 'd=' parameter, which specifies the signing domain, and can influence what's displayed or verified in relation to the sender.
   • DMARC (Domain-based Message Authentication, Reporting & Conformance): This policy builds on SPF and DKIM. It tells the receiving server what to do if SPF or DKIM checks fail (e.g., quarantine or reject the email) and provides reporting. A properly configured DMARC record ensures that aligned authentication checks (where the domain in 'From', 'Return-Path', SPF, and DKIM all align) are met.

Alignment is Key: The 'mailed-by' tag primarily reflects the domain used for the sending infrastructure. However, for the email to be considered fully authenticated and trustworthy, the domain in the 'mailed-by' field (or the domain used for SPF/DKIM checks) needs to align with the domain in the 'From' address. This alignment ensures that the email is genuinely from the domain the recipient thinks it is from. If your 'From' address is 'info@yourcompany.com' but the 'mailed-by' tag shows 'external-sender.net', it indicates a potential issue or a misconfiguration.

Who Controls It?

• Your ESP: If you use a third-party ESP, they typically manage the sending servers and will configure the 'mailed-by' tag based on their infrastructure and your domain authentication settings (SPF/DKIM). Some ESPs allow for