Check to see if there are any other SPF records in your domain’s DNS. There can only be one SPF record per domain, so if there is an existing record just add include:_spf.ariticmail.com to that record.

For example, if your domain already has the record:

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

….then you would just add:

include:_spf.ariticmail.com

The final record would look like this:

v=spf1 a mx include:_spf.google.com include:_spf.ariticmail.com ~all