I suffered from the rDNS lookup failure in the duplicate and I confirm that's fixed.
Log entry with ...ubuntu1:
May 1 09:08:36 mailout00 postfix/smtpd[30503]: connect from unknown[72.81.252.21]
May 1 09:08:36 mailout00 postfix/smtpd[30503]: setting up TLS connection from unknown[72.81.252.21]
May 1 09:08:36 mailout00 postfix/smtpd[30503]: Anonymous TLS connection established from unknown[72.81.252.21]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)
May 1 09:08:36 mailout00 postfix/smtpd[30503]: C2BD638C0FA: client=unknown[72.81.252.21]
Log entry with ...ubuntu2:
May 5 07:02:52 mailout00 postfix/smtpd[25080]: connect from static-72-81-252-21.bltmmd.fios.verizon.net[72.81.252.21]
May 5 07:02:52 mailout00 postfix/smtpd[25080]: setting up TLS connection from static-72-81-252-21.bltmmd.fios.verizon.net[72.81.252.21]
May 5 07:02:53 mailout00 postfix/smtpd[25080]: Anonymous TLS connection established from static-72-81-252-21.bltmmd.fios.verizon.net[72.81.252.21]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)
May 5 07:02:53 mailout00 postfix/smtpd[25080]: 1981238C101: client=static-72-81-252-21.bltmmd.fios.verizon.net[72.81.252.21]
I suffered from the rDNS lookup failure in the duplicate and I confirm that's fixed.
Log entry with ...ubuntu1:
May 1 09:08:36 mailout00 postfix/ smtpd[30503] : connect from unknown[ 72.81.252. 21] smtpd[30503] : setting up TLS connection from unknown[ 72.81.252. 21] smtpd[30503] : Anonymous TLS connection established from unknown[ 72.81.252. 21]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits) smtpd[30503] : C2BD638C0FA: client= unknown[ 72.81.252. 21]
May 1 09:08:36 mailout00 postfix/
May 1 09:08:36 mailout00 postfix/
May 1 09:08:36 mailout00 postfix/
Log entry with ...ubuntu2:
May 5 07:02:52 mailout00 postfix/ smtpd[25080] : connect from static- 72-81-252- 21.bltmmd. fios.verizon. net[72. 81.252. 21] smtpd[25080] : setting up TLS connection from static- 72-81-252- 21.bltmmd. fios.verizon. net[72. 81.252. 21] smtpd[25080] : Anonymous TLS connection established from static- 72-81-252- 21.bltmmd. fios.verizon. net[72. 81.252. 21]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits) smtpd[25080] : 1981238C101: client= static- 72-81-252- 21.bltmmd. fios.verizon. net[72. 81.252. 21]
May 5 07:02:52 mailout00 postfix/
May 5 07:02:53 mailout00 postfix/
May 5 07:02:53 mailout00 postfix/
So that symptom is definitely fixed.