Questions[spf](server)

This is a Canonical Question about Fighting Spam.
Also related:

• How to stop people from using my domain to send spam?
• What are SPF records, and how do I configure them?

There are so many techniques and so much to know about fighting SPAM. What widely used techniques and technologies are available to Administrator, Domain Owners, and End Users to help keep the junk out of our inboxes?

We're looking for an answer that covers different tech from various angles. The accepted answer should include a variety of technologies (eg SPF/SenderID, DomainKeys/DKIM, Graylisting, DNS RBLs, Reputation Services, Filtering Software [SpamAssassin, etc]); best practices (eg mail on Port 25 should never be allowed to relay, Port 587 should be used; etc), terminology (eg, Open Relay, Backscatter, MSA/MTA/MUA, Spam/Ham), and possibly other techniques.

This is a canonical question about setting up SPF records.

I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer connects to our mail server via IMAP using outlook. Email is sent and received by those computers, and some users send and receive email on their mobile phones as well.

I am using http://wizard.easyspf.com/ to generate an SPF record and I'm unsure about some of the fields in the wizard, specifically:

1. Enter any other domains who may send or relay mail for this domain
2. Enter any IP addresses in CIDR format for netblocks that originate or relay mail for this domain
3. Enter any other hosts which can send or relay mail for this domain
4. How stringent should SPF-aware MTA's treat this?

the first few questions i'm fairly certain about... hope i have given enough info.

Our business email is hosted on Google apps. In addition, our web server may also send email. Currently our SPF record in DNS looks like this:

domain.com.    IN   TXT    "v=spf1 a include:_spf.google.com -all"

This is all fine, however now we've outsourced our email list management to another company and we need to include a second domain with include. So, I'm looking for something like:

domain.com.    IN   TXT    "v=spf1 a include:_spf.google.com include:otherdomain.com -all"

What is the correct syntax for this? Many thanks!

I have a quick question regarding SPF records: Do they need to be present for all subdomains?

Lets say that I have a TXT record with SPF info for domain.com

Let's also say that I have a seperate email domain for subdomain.domain.com

Will the SPF policy/info for domain.com also apply to the subdomain? Or do I need to add a separate TXT record for that too?

I am looking to setup a TXT spf record that has 2 included domains... individually:

v=spf1 include:_spf.google.com ~all

and

v=spf1 include:otherdomain.com ~all

What is the proper way of combining them into a single item?