TTL Question? SMTP?

Jason Meyer · ‎03-26-2008

OK, here's question #2 for the mighty IronPort Nation. The nation is doing great so far.

I am trying to determine why an e-mail failed. The delivery failure is:

5.4.7 - Delivery expired (message too old) '[Errno 61] Connection refused'

The e-mail was sent while the recipient e-mail system was down. What I'm trying to determine is why didn't it queue up either on the sending e-mail system or on IronPort. I don't really understand the path when IronPort is involved. Anyway, my research has led me to believe the problem was caused by a TTL parameter that was too small. Do all e-mail systems use TTL? The sending e-mail system admin. says they don't have/use TTL.

Any thoughts on the topic?

Thanks,
Newbie IronPort/Messaging Admin.

Donald Nash · ‎03-26-2008

How old was the message when it expired? There is no explicit TTL mechanism in SMTP, each server retries for however long it is configured. RFC 2821 recommends a minimum retry time of "at least 4-5 days" (interesting that it is so nonspecific).

Regarding "understand[ing] the path when IronPort is involved," that's going to be very installation-specific. Your mail system may be configured to route its outbound mail via your IronPort, or it may be configured to route its own outbound mail. The fact that you got an error from the IronPort implies the former. In this case, mail will stay on the appliance for the duration of its retry time. The default is 72 hours, but can be changed via a bounce profile.

Jason Meyer · ‎03-26-2008

Thanks for the feedback!

The message expired within one minute of it being sent. It is being sent by a mainframe XMITIP application.

My path question is more related to how does an IronPort appliance handle the traffic. Is it a container, will the message actually be stored on the appliance if IronPort cannot connect to the recipient server? The recipient server was down at the time but why didn't the appliance hold onto it until it was available?

I'm scheduled for IronPort training in April.

Donald Nash · ‎03-27-2008

The message expired within one minute of it being sent.  It is being sent by a mainframe XMITIP application.

I don't know anything about that.

will the message actually be stored on the appliance if IronPort cannot connect to the recipient server?

Yes.

The recipient server was down at the time but why didn't the appliance hold onto it until it was available?

I have no way to answer that from here. My only guess is that you've altered the default retry time via bounceconfig. I suggest contacting IronPort tech support.

Jason Meyer · ‎04-23-2008

Thanks for the info....