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I am hosting an web application for many domains. The web app does send emails on their behalf. Right now, I am requiring my clients to add me onto their SPF record like a:smtp.masterdomain.com, but realized the &quot;include&quot; directive and need help making it work. The reason why I want to use the &quot;include&quot; directive is because I am adding a second smtp server that will also be sending emails for the web app, such as smtp2.masterdomain.com. I do not want to continue to ask my clients to add an smtp server every time I add one.<br />
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Say my application is hosted at masterdomain.com and is sending emails on behalf of info@domain1.com, info@domain2.com, and info@domain3.com. It is being sent by my mail servers smtp.masterdomain.com and smtp2.masterdomain.com.<br />
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Can I tell my clients to add an SPF record like: v=spf1 include:spf.masterdomain.c<wbr />om -all so I can manage the SPF records on their behalf? What would I put in the spf.masterdomain.com spf record to make the SPF pass for smtp.masterdomain.com and smtp2.masterdomain.com for sending emails for info@domain1.com, info@domain2.com, and info@domain3.com?
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I am hosting an web application for many domains. The web app does send emails on their behalf. Right now, I am requiring my clients to add me onto their SPF record like a:smtp.masterdomain.com, but realized the "include" directive and need help making it work. The reason why I want to use the "include" directive is because I am adding a second smtp server that will also be sending emails for the web app, such as smtp2.masterdomain.com. I do not want to continue to ask my clients to add an smtp server every time I add one.

Say my application is hosted at masterdomain.com and is sending emails on behalf of info@domain1.com, info@domain2.com, and info@domain3.com. It is being sent by my mail servers smtp.masterdomain.com and smtp2.masterdomain.com.

Can I tell my clients to add an SPF record like: v=spf1 include:spf.masterdomain.com -all so I can manage the SPF records on their behalf? What would I put in the spf.masterdomain.com spf record to make the SPF pass for smtp.masterdomain.com and smtp2.masterdomain.com for sending emails for info@domain1.com, info@domain2.com, and info@domain3.com?

How to centralize SPF records to one domain for multiple SMTP servers?

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

Email Servers

Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

Email Protocols

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.