Here are some examples of valid TXT values:
v=spf1 a -all ( )
v=spf1 a -all !@#$%^&*':;()_
'v=spf1 a ' -all \ foo
v=spf1 a -all \ asdf
v=spf1 a -all \\ Use of double backslash(\\) is allowed at the end.
v=spf1 a \" asdf \" -all a
Below are some examples of invalid TXT values:
| v=spf1 a -all \ | Value cannot end with a single backslash(\). |
| "v=spf1 a -all () | Double quote(") not allowed at the beginning. |
| v=spf1 a -all ()" | Double quote(") not allowed at the end. |
| v=spf1 a -all \\" | Must use single backslash to escape a double quote. |
| \\" v=spf1 a -all | Must use single backslash(\) to escape a double quote. |
| "v=spf1 a -all \_ \; \+ \^ \% " | Double quote is the only character that needs to be escaped with a single backslash. |
| v=spf1 a -all \007 | Only printable characters are allowed. Do not use escape codes to enter characters. |