Thus said [email protected] on Mon, 23 Feb 2026 12:25:22 -0500: > A more accurate description of the issue is that google and verizon > bounce mail back when there are multiple "CC" or "To" _headers_ (as > per RFC 5322), not just multiple recipients.
Yes, I've seen this (not in practice) mentioned on Google's RFC 5322 restrictions pages. They seem to be selective in which features of RFC 5322 they enforce. For example, they don't enforce the line length limit at all and gladly allow the receiving of lines that violate Section 2.1.1 Line Length Limits. In all my years of handling email I cannot recall a single time that I saw spam that included multiple To or Cc headers, so I'm curious how effective it is as an indicator and cause for rejection. The restriction apparently comes from an interpretation of RFC 5322 Section 3.6. Field Definitions which includes a table of the number of times a given header is permitted in a message. > I dunno if postfix can condense headers this way, or perhaps I can > wrap localhost:SMTP in a script (using scan & anno?!) and then send > the altered message to postfix for outbound delivery Now, for Mark's problem, I'm surprised his local postfix MSA (mail submission agent) doesn't clean up the message already. I tried sending some messages that included multiple To headers and new-inject condensed them into one To header, however, I notice that the original qmail-inject does not. Postfix should be able to handle this but I don't use postfix so someone else will have to comment---it might be possible to use a postfix "milter" to handle this. Good luck. Andy
