From: Kirill A. Korinsky <kirill@korins.ky>
Subject: Re: smtpd: implement RFC9422 LIMITS extension announcement
To: Martijn van Duren <openbsd+tech@list.imperialat.at>
Cc: tech@openbsd.org
Date: Wed, 11 Mar 2026 10:11:47 +0100

On Wed, 11 Mar 2026 00:18:24 +0100,
Martijn van Duren <openbsd+tech@list.imperialat.at> wrote:
> 
> EHLO,
> 
> While I haven't seen this in the wild, it might be nice to announce our
> limits to the world. RFC9422 specifies 3 limits that can be announced:
> MAILMAX, RCPTMAX, and RCPTDOMAINMAX. RCPTDOMAINMAX isn't a feature we
> support as far as I'm aware, but MAILMAX, and RCPTMAX are implemented,
> so why not announce them and save everybody a bit of time where
> supported.
> 
> OK?

I don't see any downside from this.

OK kirill@

> 
> martijn@
> 
> diff c2c0b9e23bf5eaddcd93c2360dcbbfbcf852c37e 5e6293dd52780ac700e0b58e520da8dec2411c56
> commit - c2c0b9e23bf5eaddcd93c2360dcbbfbcf852c37e
> commit + 5e6293dd52780ac700e0b58e520da8dec2411c56
> blob - 3dd7af8b5c6aedaf78281af00dbec916ca692db1
> blob + a41810eb6dfa5f84883d50d8541b095e2920a54c
> --- usr.sbin/smtpd/smtp_session.c
> +++ usr.sbin/smtpd/smtp_session.c
> @@ -1782,6 +1782,8 @@ smtp_proceed_ehlo(struct smtp_session *s, const char *
>  
>  	smtp_reply(s, "250-8BITMIME");
>  	smtp_reply(s, "250-ENHANCEDSTATUSCODES");
> +	smtp_reply(s, "250-LIMITS MAILMAX=%zu RCPTMAX=%zu",
> +	    env->sc_session_max_mails, env->sc_session_max_rcpt);
>  	smtp_reply(s, "250-SIZE %zu", env->sc_maxsize);
>  	if (ADVERTISE_EXT_DSN(s))
>  		smtp_reply(s, "250-DSN");
> 

-- 
wbr, Kirill