I sent an important email to my collection agent 2 weeks ago and since I didn't receive a bounce I assumed it reached him successfully.

About a week later I called him to discuss the matter further and he said he'd never received my email.

I sent it again and this time he received it immediately, but by then the issue had become moot.

Today (2 weeks after sending the message) I received a bounce from his mail server which had rejected my message due to the Grey Listing system that they have recently employed.

How the hell can you do business via email when Grey listing plays silly buggers with your messages?

Will we have to start ringing people after we send each email to make sure they received it?

Request a delivery/read receipt for your emails. If you don't receive one within 48 hours and you think they should've read it within that time frame, then yes, give them a call.

It's annoying how people rely on email as an instant method of communication and have a hissy fit when things don't go correctly.

Ask them to whitelist your domain/email address.

Their greylisting system should've told you within 24 hours that it had been delayed.

Are you using an internal mail server to send out directly, or are you relaying your mail through your ISP? You should consider doing the later, as it will reduce your chance of being greylisted and should automatically re-send the email, should it be greylisted.

...unless you're doing it the other way and your mail server is to blame...

Yea, Greylisting is a pain and seems a bit hit and miss.

We used it as a part of our overall spam filter, didn't work out as customers didn't understand they had to use our mail server to allow the server to build white lists of the people they send email too (for example the server would trust the addresses of anyone you send mail to so their reply's won't be delayed, however if you used your ISPs server it wouldn't work because it wouldn't know about it )... We've since stopped using it and are building our own mail scanner using MailScanner and Spam Assassin.

Actually it'd be up to your own mail server to tell you that it hadn't been delivered yet......all greylisting issues that I've seen are due to the sender's side being 'out of the ordinary'.

We ended up going the route of greylisting RBL'd IP's only as there were a handful of major webhosters that were 'out of the ordinary'. We found most ISP's surprisingly play ball rather well with greylisting.

That will only work if people have their email clients set to send a response to read receipts. I don't - it's nobody's business when I read their emails.

This is the 21st century, email is a commonly accepted form of instant communication. I have never had a problem like this before - it seems greylisting is the factor that caused the problem.

I don't need to do this now - subsequent emails have arrived without any problem. It was just the first email that I sent after they switched to the greylisting system that had the problem.

It should have. That would have been much more helpful. In fact, an immediate response would be more professional.

I use my ISP (Optus) smtp server (unless it's down and then I use my own)

Maybe I should stop using the Optus SMTP server and just use my own.

I use MailScanner and Spam Assassin on my primary mail servers and Spam Assassin alone on my secondary MX servers and it works an absolute treat.

I publish my email address on my website which means it's easily harvested by the spam bots and I get an average of 2 spam messages per week.

The only ones that get through are the ones that use a new terminology or a new technique, but spam assassin catches on very quickly.

I cannot speak highly enough of the MailScanner/Spam Assassin/ClamAV system - and it's free.

Umm,

It's worth pointing out here that if your server has been permanently greylisted the receiving mail server is more than likely broken in some way. Greylisting sends a temp fail and is SUPPOSED to be reenabled within an hour or so (in time for the next retry). If you didn't get the 'hey this is broken' email for 48hrs chances are the receivers mailservers are misconfigured.

Greylisting is highly effective but definitely a bit hit and miss. It gets rid of most of the crap though (on a large installation we were getting about 100,000 messages per day, this dropped to just 10,000 msgs once greylisting was put in) and realistically, the msg working Greylist installs spits out should be a TEMP failure for a limited period of time.

Stu

I'd say you don't get enough messages.

We have multiple MailScanner installs but it's accuracy for large numbers of mailboxes (ie. when you just want a global rule set) leaves a bit to be desired.

We've opted for the option of replacing our anti-spam infrastructure with IronPort C350 devices. With reputation filtering alone we've found we drop about 99% of crap (about 500K attempts a day).

Stu

We use Ironport as well as can’t speak highly enough about them…. It regularly receives updates every hour or more from the reputation database along with live virus out break filters it’s an appliance I recommend to anyone, although it is expensive.
Trend Micro make a nice product also called the IGSA which we tried this for awhile but went with Ironport in the end.

Regards James

The way greylisting is meant to work is that it returns a temp fail for a connection attempt from an "unknown" sender (or server). When working, it remembers the initial connection and allows a retry to succeed. No email should ever be lost or bounced.

This is simply relying on the fact that spammers rarely retry as they have very limited time to get their messages out before they get into RBLs etc.

Lots of greylisting implementations are broken though, and it sounds like the OP's system was badly broken.

Interesting to hear how successful the Ironport devices are!

There was an interesting talk at the recent SAGE-AU conference on encrypting email address on webpages automatically. The idea was that a filter in Apache would encrypt any email addresses in webpages to prevent spammers harvesting them. Very interesting concept; if nothing else it could reduce the load on your server (or ironport) quite significantly over time as the majority of spam seems to come from web page email address harvesting.

RBL + Spam Assassin + MailScanner is a perfect combo. The only spam I get now is that stupid we couldn't deliver your parcel emails from American courier companies...

You gotta use triple bags man otherwise the couriers decide to take their cut.

Joke of course.

Stu