Re: quota-status fails when size=0 from Postfix

At least from Thunderbird, yes. But SIZE=… does not seem to be a mandatory addition to the RCPT-TO line. Perhaps other mail clients do not use SIZE either. Just guessting.

http://www.postfix.org/SMTPD_POLICY_README.html The "size" attribute value specifies the message size that the client specified in the MAIL FROM command (zero if none was specified). With Postfix 2.2 and later, it specifies the actual message size after the client sends the END-OF-MESSAGE.

Okay, it looks like if you are using an old version of postfix then postfix does rely on the client telling it the size of the email. But with postfix version 2.2 or newer postfix computes the size itself.