sendmail error 503 5.0.0 Need MAIL before RCPT

[beckas]

Hi

I am not familiar with sendmail at all (I am a Microsoft Exchange
Administrator) so I really need some help from you experts. My
company is not able to send to another company that uses sendmail as
their e-mail platform. We receive the following bounce back message
when mailing to them:

Unexpected recipient failure - 503 5.0.0 Need MAIL before RCPT

The sendmail e-mail administrator swears that there is not a problem
with his server and that it's a problem on my side yet I sent them the
dialog that my e-mail server had with his and the dialog states that
the message was passed to his e-mail server.

Now I don't understand how sendmail resolves but I'm guessing that
these people don't have the 'accept_unresolvable_domains' enabled on
their sendmail server and their server is not resolving my domain. If
this is the case, how does sendmail resolve a domain? Does it only
use DNS recors? I ask because my domain is configured not to reply to
ping requests for security reasons. I am not aware of any DNS
misconfigurations with any ISPs in regards to my company.

Funny thing is that the sendmail administrator rebooted his sendmail
server the other day and things were temporarily fixed for a day. Now
the problem is back again.

Can anyone give me some advice on what I should do to troubleshoot
this? I'm really frustrated that the sendmail administrator is making
this my problem and does not have any knowledge on how to troubleshoot
this problem.

Thanks,

Rebekah

 

[DumTech]

I usually get different errors when DNS is to blame for a Sendmail problem (which has caused me a bit of trouble). The 'Need MAIL before RCPT' isn't what I'd expect, as it refers to the most basic of SMTP stuff... You say HELO [host.domain.tld] (or EHLO (for ESMTP, I think?)), MAIL FROM: [sender address], RCPT TO: [recipient], then DATA [and the message body].

The error message you're getting is what you get if you send the recipient before the sender's address, as below.

RCPT TO: fred@barney.com
503 5.0.0 Need MAIL before RCPT

That said, the only time I've ever seen that error is when I have been sending mail 'manually' (telnet port 25) just for 'educational kicks' and forgot to give MAIL first.

Perhaps it could stem from a DNS resolution failure though... Maybe see what you get directly from Sendmail when you telnet to port 25 on the other server and attempt to send a test message...? Matt
matt@paperlove.org
If I can help, I will.