Random results on both stream and datagram

[soywod]

When sending a basic MX question using new base API, I don't always get the same result. For example, querying domain posteo.net against Google's DNS 8.8.8.8 gives sometimes this result:

Got a question: Question { qname: RevName(.de.posteo), qtype: QType::MX, qclass: QClass::IN }

Sometimes this other result:

Got a question: Question { qname: RevName(.de.posteo), qtype: QType::MX, qclass: QClass::IN }
Got an answer record: Record { rname: RevName(.de.posteo), rtype: RType::MX, rclass: RClass::IN, ttl: TTL(42), rdata: Mx(Mx { preference: U16(10), exchange: Name(mx04.posteo.de.) }) }
Got an answer record: Record { rname: RevName(.de.posteo), rtype: RType::MX, rclass: RClass::IN, ttl: TTL(42), rdata: Mx(Mx { preference: U16(10), exchange: Name(mx02.posteo.de.) }) }
Got an answer record: Record { rname: RevName(.de.posteo), rtype: RType::MX, rclass: RClass::IN, ttl: TTL(42), rdata: Mx(Mx { preference: U16(10), exchange: Name(mx01.posteo.de.) }) }
Got an answer record: Record { rname: RevName(.de.posteo), rtype: RType::MX, rclass: RClass::IN, ttl: TTL(42), rdata: Mx(Mx { preference: U16(10), exchange: Name(mx03.posteo.de.) }) }

No matter if I use TCP stream or UDP datagram. Is it normal in DNS world? Do I miss sth?

[soywod]

I think I got my answer over time: Recursion Desired seems to be often required by servers. Without it set to true, it gives random results for MX, and 0 results for TXT or SRV. Good to know ;)