Evgeniy Berdnikov <b...@protva.ru> (Mi 18 Jan 2017 21:56:49 CET): … > > - I'll start with: you don't want it at RCPT or earlier > > because that will impact sender-verify callbacks. > > Exactly. Session with "MAIL FROM: <>" may be a sender verification > callback, so in this case we want to send clear 2xx responses to RCPTs > as client expects, suppressing 4xx codes from greylisting engine. > That's why greylisting is postponed until DATA command received.
Ah. Got it. Thank you. Side note: we should have: --> MAIL FROM:<> <-- 250 OK --> VRFY f...@example.com <-- 250 OK f...@example.com accepts mail from <> --> QUIT This would avoid all that clumsy sender-verification-de-impact hacks. > > What should be preferred practice > > when CHUNKING is used? > > With BDAT syntax we have to mix "pre-data" and "post-data" approaches. > Unfortunately, this way conflicts with RFC3030 which states: … > A 250 response MUST be sent to each successful BDAT data block within > a mail transaction. If a failure occurs after a BDAT command is > received, the receiver-SMTP MUST accept and discard the associated > message data before sending the appropriate 5XX or 4XX code. If a …. > So the "legal" way is to postpone 4xx response until the completion of > data stream. The protocol design is nasty. To overcome it one can violate > RFC3030 and send 4xx response to the first BDAT. However, there is more > efficient way: server can close socket on the receipt of BDAT, client > should get EOF and process such transmission error as receipt of 4xx. :) > Sounds funny, yes, but can be implemented in Exim as conditional "drop" > in acl_smtp_bdat (to be executed on first BDAT command). Both can probably be combined, send the illegal 4xx response after the first BDAT chunk AND drop the connection *if* the client continues sending or shutdown gracefully if the client handles the illegal 4xx and sends a QUIT Best regards from Dresden/Germany Viele Grüße aus Dresden Heiko Schlittermann -- SCHLITTERMANN.de ---------------------------- internet & unix support - Heiko Schlittermann, Dipl.-Ing. (TU) - {fon,fax}: +49.351.802998{1,3} - gnupg encrypted messages are welcome --------------- key ID: F69376CE - ! key id 7CBF764A and 972EAC9F are revoked since 2015-01 ------------ -
signature.asc
Description: Digital signature
-- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/