What order do split TXT records get assembled in?
Solution 1:
The parts are always reassembled in order. The 255 character limit is on parts of the TXT record. Without EDNS0, there is an addtional 512 byte limit for a UDP response. However, this does not apply to a TCP response.
Solution 2:
Also, you may encounter a problem with AWS Route53, where
IN TXT "v=spf1 .... first""second string..."
IS treated as an equivalent to
IN TXT "v=spf1 .... firstsecond string..."
But if you use spaces... the following WILL FAIL:
IN TXT "v=spf1 .... first" "second string..."