Description of domain with many mail servers

[subornaakter20]

The RFC states that a single record after concatenation should be 450 bytes or less. It is not recommended to write a record longer than 450 bytes, but if one SPF record consists of multiple character strings, the receiving side will concatenate all the character strings and process them as a single string for authentication.

Note, however, that when multiple strings are concatenated into a single string, no whitespace is inserted between the strings.



Common mistakes with SPF records and how to fix them
As explained above, there are various ways to write medical practice email list SPF records. Therefore, it is easy to make a mistake, and if you publish an incorrect SPF record, the receiving side will treat it as a PermError and will not be able to authenticate correctly.

Below are some examples of common mistakes.



① The version is incorrect.
[Incorrect] example.co.jp. IN TXT "v=spf1.0 include:spf.example.jp ~all
[Correct] example.co.jp. IN TXT "v=spf1 include:spf.example.jp ~all
Please make sure to write the SPF version as "v=spf1".



② Cases where the mechanism is omitted
[Incorrect] example.co.jp. IN TXT "v=spf1 mx01 mx02 ~all"
[Correct] example.co.jp. IN TXT "v=spf1 +a:mx01.example.co.jp +a:mx02.example.co.jp ~all"
Do not omit the mechanism; be sure to use the FQDN and write it as "+a:hostname(FQDN)".