Milter-greylist

I’m troubleshooting a blocked email and noticed that the ‘from address’ looks like it is getting truncated at an ‘=‘ , and getting snagged by the rule:
    /^<?planx\.com.+\@.*$/ \ # fake username


Per https://en.wikipedia.org/wiki/Email_address#Local-part
the equal sign is a special character, but is allowed.

Am I missing something or was this overlooked?

Bill

Log:
/var/log/maillog-20180510:May 10 02:56:09 mail milter-greylist: w4A2u4ZD015699: addr [167.89.58.195][167.89.58.195] from <planx.com@...> to <sleve@...> blacklisted (ACL 2880)
/var/log/maillog-20180510:May 10 02:56:23 mail sendmail[15699]: w4A2u4ZD015699: from=<bounces+5356899-9561-sleve=planx.com@...01.wixshoutout.com>, size=0, class=0, nrcpts=0, bodytype=8BITMIME, proto=ESMTP, daemon=MTA-v6, relay=o21.sg.wixshoutout.com [167.89.58.195] (may be forged)