I realize similar questions were asked/answered on this, but I have a subtle detail to which I can not find answers anywhere. Let's exemplify with the following DNS entries:
foo.example.com A 220.127.116.11 bar.example.com A 18.104.22.168 wee.example.com CNAME foo.example.com foo.example.com MX foo.example.com.s9a1.psmtp.com bar.example.com MX bar.example.com.s9a1.psmtp.com
Note the last line. My institution has that kind of MX records, where for each MX record the value has the label prepended. Question 1 is, what is the motivation for this (why not just s9a1.psmtp.com)? Question 2 is more subtle and follows..
My understanding is that an MX record should not contain any aliases for neither label nor the value, i.e. the following would be bad practice:
wee.example.com MX wee.example.com.s9a1.psmtp.com
Then, how should the RRs look for the alias