Does a sending IP address need to accept incoming SMTP connections for email deliverability?
Summary
What email marketers say8Marketer opinions
Email marketer from Stack Overflow clarifies that outbound SMTP servers are not required to accept incoming SMTP connections. Focus should be on outbound connectivity and DNS records.
Email marketer from Reddit shares that a sending server does not need to accept incoming SMTP connections. The important aspect is that the server can initiate outgoing connections to other mail servers.
Email marketer from SendGrid explains that deliverability depends on factors like sender reputation, authentication (SPF, DKIM, DMARC), and list hygiene. The ability to accept incoming SMTP connections on the sending IP is not listed as a requirement.
Email marketer from Quora explains that the sending IP doesn't need to accept incoming connections. What matters is the ability to send emails out and proper authentication.
Email marketer from Mailjet shares that the sending IP does not need to accept incoming SMTP connections. Mailjet handles the SMTP infrastructure. Users only need to configure their sending domain.
Email marketer from Reddit responds that focusing on the sending IP accepting incoming connections isn't relevant. Instead, ensure your domain has valid SPF, DKIM, and DMARC records.
Email marketer from Email Geeks explains that checking if something can receive mail is done on the domain level, not IP. The IP you are sending mail from doesn’t necessarily need to receive stuff. Some might check if the domain they receive mail from can in fact receive email by checking the MX record.
Email marketer from Neil Patel's Blog shares that while IP reputation is crucial for deliverability, whether an IP accepts incoming SMTP connections is not a direct factor. Focus should be on maintaining a good sending reputation through authentication and engagement.
What the experts say5Expert opinions
Expert from Email Geeks says that this is the first she’s ever heard of requiring the sending IP to accept connections on port 25, and that they've been sending from an IP that doesn’t receive email for at least 5 years.
Expert from Email Geeks shares that only the tiniest misguided email domains are worried about connecting back to your IP on port 25, stating that any real ISP or anyone with expertise would know it’s a useless check.
Expert from Email Geeks states that the check is actually if the domain has an MX record and the MX accepts mail, not the sending IP.
Expert from Word to the Wise responds that while reverse DNS is important for IP reputation, accepting inbound connections on port 25 is not usually a requirement for sending IP addresses to achieve good deliverability.
Expert from Spam Resource explains that a properly configured outbound SMTP server primarily needs to establish connections to recipient mail servers. It doesn't require accepting inbound SMTP connections for deliverability.
What the documentation says3Technical articles
Documentation from RFC Editor explains that SMTP is primarily a push protocol where the sending server initiates the connection to the receiving server. There is no requirement for the sending IP to accept incoming SMTP connections.
Documentation from SparkPost explains that the focus should be on configuring SPF, DKIM, and DMARC properly. Accepting inbound connections on the sending IP is not mentioned.
Documentation from Microsoft Learn explains that SMTP servers typically do not require accepting incoming connections on port 25 for outbound email delivery. The primary function is to establish outbound connections to recipient mail servers.