I am sorry that I did not have time to address this problem this week. I will unfortunately be on vacation next week, and at a hackathon the week after that. I will make time to fix this as soon as I can, but it will likely be awhile yet.
I do not know why email is suddenly crapping out so completely, although I did do an analysis a couple of days ago using mail-tester.com. It discovered the following issues:
Your message is not signed with DKIM
DomainKeys Identified Mail (DKIM) is a method for associating a domain name to an email message, thereby allowing a person, role, or organization to claim some responsibility for the message.
You do not have a DMARC record
A DMARC policy allows a sender to indicate that their emails are protected by SPF and/or DKIM, and give instruction if neither of those authentication methods passes. Please be sure you have a DKIM and SPF set before using DMARC.
You do not have a DMARC record, please add a TXT record to your domain _dmarc.imagej.net with the following value:
mail-tester.com; dmarc=none header.from=imagej.net
From Domain: imagej.net
Your reverse DNS does not match with your sending domain.
Reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address.
Some companies such as AOL will reject any message sent from a server without rDNS, so you must ensure that you have one.
You cannot associate more than one domain name with a single IP address.
Your IP address 220.127.116.11 is associated with the domain wmmta5.doit.wisc.edu.
Nevertheless your message appears to be sent from smtp8.wiscmail.wisc.edu.
You may want to change your pointer (PTR type) DNS record and the host name of your server to the same value.
Here are the tested values for this check:
You’re listed in 1 blacklist
Matches your server IP address (18.104.22.168) against 21 of the most common ipv4 blacklists.
Listed in SORBS-SPAM
It also originally complained about a missing SPF record, but I fixed that one.
In order to avoid the reverse DNS and blacklist issues, it may be simplest to switch away from the UW-Madison’s mail server in favor of the one we run at LOCI, since I have no control over the former’s configuration.