Bad addresses, Quarantine, Hard Bounces, Soft bounces

What is a Quarantined address? = Email is invalid    

Ofsys automatically puts addresses in uarantine when Ofsys receives 100% information, from destination servers, that this address is not valid.
Quarantaine means, « this mail address does not exist: "Ofsys spoke to the server and we are convinced that this address doesn't work and will never work.».

A contact that is in Quarantine is not de-activated in Ofsys, it will no longer receive messages and if its Email address is corrected, he will resume to receive messages.
If our clients are interested in knowing more about which contacts have been placed in Quarantine, then in addition to the interface "invalid emails" section, they should look in our daily exported CSVs, in the CSV dedicated for Contacts and look for field : « isInvalidMailbox » is equal to « 1 » if we are certain that the address is wrong. Our clients could ask a new email address to their clients when they come back to the website or call the company or receive a call from the company.


Bounces (Soft and hard) = Server refuses the Email

It means that the message was not delivered but it's for another reason than the validity of the email address. In other words, all other reasons that a message cannot be delivered EXCEPT « the account isn't good ». Examples : Full mailbox: generally a hard bounce, but of course temporary (tomorrow, it might work).  Content rejected by spam filter, it will also be a hard bounce, but next message could very well be accepted.  Serveurs full, the destination server could be in temporary troubles. Hard bounces and Soft bounces do not have any connections with the concept of "the address isn't good".  So, a bounce that doesn't put the contact in quarantine means that "the message could not be delivered for X reason but the address is probably right". The problem is something else.
Hard bounces « Hard bounce » are all « 5xx » answers from SMTP servers. It's a mechanic that says "Don't try to send me this message, I don't want it". But it has nothing to do with the validity of the Email address. How does Ofsys manages errors? We work with our mechanism of Quarantines. Ofsys is completely automated and transparent for our clients. We analyse EXACT responses from servers of major Webmail clients and well known SMTP types and we put as quarantine, all emails that are recognized as invalid (account terminated, unknow user, etc...). Our system eliminates 99% of bad addresses and the rate of false positives is extremely low : less than 1 on 1 million. Our clients ignore the management of bounces and this is what we recommend, Ofsys will manage.


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    Ofsys Master


    5.x.x doesn't necessarily mean that the email address isn't good.  There are probably more than 50 such variations which are just normal errors and only a few that cause a quarantine (specifically, the majority of 5.1.*). Please consult the Microsoft knowledge base which summarizes these codes :

    As far as Ofsys rules putting email addresses in quarantine, it's not really possible to put in a simple documentation because these rules change all th etime because they adapt very fast with a changing environment. What makes those rules change so fast :

    • Rules changes at major ISPs
    • Rules updates in major large companies (like Exchanges or Lotus notes)
    • New ISPs on the market
    • New recurring errors that we discover and for which we create new rules


    At present, there are more than several HUNDREDS or rules to put an email address in quarantine.  Such rules (for as an example) look like :

    • For the « MX » for which domain name ends with « »,
    • Whenever the initial SMTP response is known like a « 5.0.0 » (i.e. when the server returns an SMTP error in the  « 500 » without giving a DSN code),

     Then the following « REGEX » matchs will be converted like:



    ^503 Valid RCPT command must precede   DATA$




    ^550 Message was not accepted -- invalid   mailbox.$




    ^550 must be local recipient$




    ^550 you have exceeded message receiving   limit for user.*$





    Reasons :

    • 5.1.3 = incorrect email syntax. judges the email address as invalid while OUR servers know that it's a legitimate Email address.  Causes a Quarantine.
    • 5.1.1 = mailbox invalide. Standard qurantine.
    • 5.7.1 = « Delivery not authorized, message refused ». Classical case « system refuses to relay this message », typically because this address isn't local. We'll have a kind of "random" validation between 5.1.1 et 5.7.1 in many cases, it all depends on how the "IN" systems of ISPs will work (sometimes our server speak with one intermediary server that will ask another sub-system and it answers 5.7.1 because it cannot relay, other times, it answers 5.1.1... there's no uniform standard as you can see.. Causes quarantine in this case.
    • 5.2.0 = conversion of this error to another more precise code, in order to clarify that it's a mailbox error (in the same principle as the « mailbox full » etc. Doesn't cause a quarantine

    Our engineers analysze, on a weekly basis all the "non-qualified" messages for ALL ISPs (majors and very small) and new rules appear or dissapear accordingly.  It's a permanent adaptative process that require several sull-time human resources just for controlling and adjusting those rules.

    The important point here to remember and assimilate is that quarantine has NOTHING to do with a process that de-activate contacts which have experienced hard bounces.

    The goal here is to simply stop sending to email addresses for which we have received a VERY CLEAR and DEFINITIVE answer from the destination server which manages the respective domain. This email address doesn't correspond to a mailbox capable of receiving the Message, so there's no need to send again. .

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