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SPF Records Question

Ok - I'm a little confused by SPF records.  So - help me out :)

Let's say I set up a pretty strict set of SPF rules on my domain.  Will that have any impact upon my ability to send mail from various locations via thundbird, outlook, etc?

I wouldn't think so, correct?  Or - am I wrong?  Would a fairly strict set of SPF rules confine me to only being able to send mail from specific locations via a normal email client?
3 Solutions
SPF records only affect the server listed in the domain as the mail exchanger (MX).

The mail server does the sending and receiving, your client just bounces off of it (SMTP out)  or receives from it (POP IMAP etc in), so it is still only seen as coming from the mail server's ip address, which is used in the MX record and SPF rules apply.

So correct, it would not have any impact on your ability to send mail from various locations.
erzoolanderAuthor Commented:
So - for the purposes of explaining it to my client...

Messages sent via Outlook/Thunderbird are actually seen by the server as being generated from it's own IP address due to login.  Therefore they are unaffected.

SPF records records, essentially then, are a list of mail exchanges that may send email with that domain name.

(lol, i keep saying SPF, like sunscreen)

Yes, how ever you connect to your mail server is just that.. a connection to the mail server.

The mail server for your domain is the responsible Mail Exchanger for that domain(s) and the IP address of that mail server in the mx record, as well as the parameters in the SFP record, are all the outside world ever sees or cares about.

Yes, SFP records are a way to allow reverse checks of the sending domain (your mail server) to be more lenient than a strict reverse lookup. This allows for ranges of ip addresses, multiple host names, etc.
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Some of this requires clarification.
SPF and MX records are not necessarily related, although they often are.  MX records tell other mail servers which servers to contact in order to send mail TO your domain; SPF records list the servers that are allowed to send mail FROM your domain.  Often these are the same servers (in which case "v=spf1 mx -all" is all you need in your SPF record), but they don't have to be.
You will need to setup the clients to send email through your smtp servers (servers that are listed in SPF records).

Remote clients that use third party smtp server to send emails will be treated as spam by receiving servers that are configured to check spf records.
erzoolanderAuthor Commented:

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