An SPF record for a single domain looks like this:
"v=spf1 include:spf.protection.outlook.com -all"
If you have a web server out on the internet that is sending mail on your behalf you may need to add another domain to be included in this SPF record. To add the second domain you need to amend it like this:
"v=spf1 include:spf.protection.outlook.com include:example.co.uk -all"
To add a specific IP address this will work:
"v=spf1 a ip4:123.123123.123 include:spf.protection.outlook.com -all"
SPF Record for AVG-AntiSpam
"v=spf1 ip4:100.42.120.96/27 ip4:100.42.115.0/27 ip4:208.70.208.0/22 ~all"
SPF Record for AVG-AntiSpam for Office 365
v=spf1 ip4:100.42.120.96/27 ip4:100.42.115.0/27 ip4:208.70.208.0/22 a include:spf.protection.outlook.com ~all
SPF RECORDS MUST BE ENCLOSED IN INVERTED COMMAS “” “” “”
SPF Record Generator – http://www.mailradar.com/spf/