Re: SNDDST works while QTMMSENDMAIL is blocked from relaying

John,

SMTP delivers e-mail based on the domain in the destination e-mail address. So if your e-mail address is jdoe@xxxxxxxxxxx, it takes the part after the @ symbol (example.com) and does a DNS lookup on it. First, it looks for MX records for example.com. If no MX records exist, it looks for the A record for example.com.

It sorts the MX records by priority, and then goes down the list until one of them responds. Then, delivers the message to that server. If no MX records, it contacts the host identified by the A record directly. In both cases, if nothing responds, it puts it in a queue and tries again later.

That's the normal way SMTP works. But sometimes, folks want all of their e-mail to go through a particular mail server. This might be because that mail server is the only one authorized to send mail through their firewall. Or it might be that the IP address assigned to their i is "dynamic", and therefore other SMTP servers might not accept mail from them (due to spam blocking.) In cases like these (which, in my experience, are the majority of IBM i shops) you configure the FIREWALL/MAILROUTER parameters to forward the e-mail to a specific server. (Or, on new releases, consider FWDHUBSVR instead.)

However, I don't understand this tangent to the conversation, since these parameters apply equally to SNDDST and QtmmSendMail! Both go through the same SMTP server.

One big diff between SNDDST and QtmmSendMail is that with QtmmSendMail, you code the e-mail headers yourself. With SNDDST, the system supplies them for you. Not exactly sure how this might relate to the issue, but it's really all I can come up with at this point.


On 12/23/2010 8:13 AM, John Allen wrote:

Thanks for the info.

Looking at CHGSMTPA attributes it shows MAILROUTER= *NONE, given this, how
does it resolve to the email server to use?

Thanks

John