SPF is an email authentication protocol. Pobox participated in its creation -- it was started by our founder, Meng Weng Wong. Neat!
SPF lets domain owners specify a list of servers that it approves to send mail from their domain. It also lets them say what recipients should do with mail claiming to be from their domain that doesn't come from the listed servers. It's best suited for domains that always know where their mail is coming from -- generally businesses or large organizations.
SPF is not well-suited for domains that don't always know where their mail is going to be sent from. An inaccurate SPF record can cause ISPs to treat your mail as spam, or even bounce it. For that reason, we don't recommend it for all domains. Please use caution when setting up an SPF record.
Do you, and all your users, send mail through the Pobox SMTP servers? If so, turning on SPF is unlikely to disrupt your mail.
Do you sometimes send mail from your ISP? Have webmail (other than Pobox's) set up to send mail from your domain? Use scripts or programs on your website to send mail from your domain? Host a mail server on a line without a static IP address? We don't recommend SPF for your domain.
The one exception: If you send mail from an email marketing provider (like Constant Contact, or Listbox, or one of many others), your SPF record is unlikely to cause a problem for that mail. Most legitimate email marketing providers use an "envelope sender" at their own domain, which uses their SPF records, not yours.
Go to your domain's MyPobox page. If you see a section in the right bar labeled "Pobox SPF", we host your domain's DNS, and you can set up an SPF record saying all mail from your domain will come through our SMTP servers. Clicking the button in that section will create the record. These records are not editable, and cannot be added to.
You can add Pobox's SPF record to the record for your domain, which will automatically include our most up-to-date information about our SMTP servers. Just add: