Had an interesting issue where a remote mail server was responding in its EHLO that it supported DSN, but would not send successful DSN reports as requested. In order to work around the issue I just configured Postfix to ignore the remote mail server’s DSN support:

/etc/postfix/dsn_override:
1.2.3.4 dsn

postmap /etc/postfix/dsn_override

/etc/postfix/main.cf:
smtp_discard_ehlo_keyword_address_maps = hash:/etc/postfix/dsn_override

Successful “ignoring” should look like this in the maillog:

Nov 30 18:33:33 bigbertha postfix/smtp[22632]: discarding EHLO keywords: DSN