Hello, and welcome!
First, you may want to edit your initial post and redact your personally identifiable information. But, since you provided it, I'm able to see that your local computer "ithaca," when using your fully qualified domain name -- is not resolvable by an authoritative server on the Internet's Domain Name System (DNS). Because it isn't resolvable, that machine cannot be found on the Internet, and its responsible mailserver cannot be identified -- since there is no record of the domain, it doesn't have any MX mailserver records.
To see every type of DNS record for the higher level domain name's records, which do exist, remove "ithaca." from the front of the domain name and use:
$ dig <domain name> ANY
The MX record reports the mailserver used to email users @<domain name>. Note also, the reported status is "NOERROR" -- no errors during the query.
If you are using your ISP's nameservers, or other external nameservers, try the command, this time adding "ithaca." in front of your domain name. The response will show which nameservers at your ISP are authoritative, and the reported status will be "NXDOMAIN" - domain name not found. You'll also note, no MX record, since no records at all are available.
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