Empty envelope sender is rejected

[wttw]

Inbucket rejects mail sent with an empty envelope sender.

MAIL FROM:<> is valid in SMTP, and sometimes used for low-value mail (out-of-office, receipt notifications, etc) to ensure that failed delivery will be discarded rather than causing an asynchronous bounce, and to mitigate some flavours of mail loop.

It's a very minor issue, but if fixing it were as simple as removing a check or changing a regex it'd be nice to do.

[9:44:34.675 8] Starting SMTP session
[9:44:34.676 9] <<< 220 inbucket Inbucket SMTP ready
[9:44:34.676 9] >>> EHLO abacus
[9:44:34.676 9] <<< 250-Great, let's get this show on the road
[9:44:34.676 9] <<< 250-8BITMIME
[9:44:34.676 9]     250 SIZE 10240000
[9:44:34.676 9] >>> MAIL FROM:<>
[9:44:34.676 9] <<< 501 Was expecting MAIL arg syntax of FROM:<address>
[9:44:34.676 9] >>> QUIT
[9:44:34.677 9] <<< 221 Goodnight and good luck

[jhillyerd]

I expect having a null from will cause a lot of problems internally, but perhaps it can just be set to unspecified at the time it's received so there is some value for the UI to display.