Webmail wont send emails to valid emails on a distribution list if one email address is invalid

[pa1]

With both Webmail  POP and exchange accounts if just one email address on a distribution list is invalid a message sent to that list won't be won't be delivered  to both all valid and invalid email addresses. In other words if just one email on the list is invalid the message gets sent to no one on the list whether valid or invalid.

And with the rejection of all addresses the following message is sent to the sender:  "This is the mail system at host cds213.dcs.int.inet.  The email cannot be sent because at least one address is not valid:"
This is a new development, previously Webmail would attempt to send the email to all recipients in the list. If it encountered an invalid email address among the recipients, it would send the email to the valid recipients and generate a non-delivery report (NDR) or bounce-back message for the invalid recipient.

Anyone have a fix for this

Thanks

[mdk]

@pa1 -- Anyone have a fix for this?

I like the new processing that Shaw's mail-servers are doing. For me, it's simpler to get the "rejection" message, fix/remove the "bad" ID, and re-send the message to all the recipients, than it would be to receive multiple NDR reports, and to one-by-one handle each ID.

Of course, if you send to "badfe11ow@telus.net", when the real ID is "badfellow@telus.net", it will be the Telus mail-server that would receive the message, declare it as "unknown recipient" and send a NDR to you.  That is different than Shaw's mail-server immediately recognizing that "badfellow@te11us.net" is not a known domain-name, and refusing to send anything to all your recipients.

In short, I see nothing that needs "fixing".  YMMV

[pa1]

When faced with an outdated email mailing list consisting of 50 or so email addresses how does one determine which one or more of these is invalid. Are you saying you would have to go through the whole list by hand and if you don’t spot anything obvious you might have to generate a test email to each or start in groups say half first, half second and so on? On the other hand, wouldn’t it be simpler if Webmail would flag the bad ones at the initial send of the email. Perhaps there is software that will go through the list and find the bad ones. Any SW you know of? And of course, all of this predicated on the fact that the good email addresses are going to be annoyed with test messages.

As regards your example of badfe11ow@telus.net, you are saying that shaw web mail actually sends it to the telus mail server and you get an NDR back.  But what about the good email addresses on the list, does it send the email to the other good addresses on the list too.  From what I understand Shaw web mail wouldn't send it to anyone on the list, if just one is bad.  And what about mail servers other than telus, are they all required to send an NDR back?

In essence I understand from you that Shaw’s mail servers have recently changed to this non NDR report system. It presents an new challenge and I am searching for a workaround.
Thanks for any suggestions.

[mdk]

@pa1 -- 

When faced with an outdated email mailing list consisting of 50 or so email addresses how does one determine which one or more of these is invalid.

There are multiple levels of "invalid" and/or "bad".

When you send your message to Shaw's mail-server, for intended delivery to your list of IDs, that mail-server does an immediate check of each ID, to see if the domain-name is valid, i.e., if there does exist a mail-server that, for each ID, will receive the message.  Example:

$ nslookup -type=mx sshhaaww.ca
*** can't find sshhaaww.ca: Non-existent domain

The "MX" record(s) are set by the recipient's domain, to identify the mail-servers within that domain. Example:

$ nslookup -type=mx gmail.com

gmail.com MX preference =   5, mail exchanger = gmail-smtp-in.l.google.com

gmail.com MX preference = 10, mail exchanger = alt1.gmail-smtp-in.l.google.com

gmail.com MX preference = 20, mail exchanger = alt2.gmail-smtp-in.l.google.com

gmail.com MX preference = 30, mail exchanger = alt3.gmail-smtp-in.l.google.com

gmail.com MX preference = 40, mail exchanger = alt4.gmail-smtp-in.l.google.com

The values of "preference" define the order in which Shaw's mail-server will try to connect to GMail's fleet of mail-servers.  When one mail-server does not respond, Shaw's mail-server tries the next.

If even ONE of your IDs is invalid, then the Shaw mail-server will immediately return your complete message to you.  It will not attempt to deliver the message to the valid IDs.

The second level of "invalid" is when one of your IDs references an "@shaw.ca" ID that does not exist. The Shaw mail-server does this check, because it is a Shaw ID that will get "local delivery".

The third level of "invalid" is when the recipient's mail-server, e.g., the server receives a message addressed to "username@gmail.com".  If "username" is not a valid ID within the "@gmail.com" domain, then the mail-server will send an "undeliverable" or "non-existent ID" error-message back to your ID.

Thus, you will learn that one ID on your list is not valid.

On the other hand, wouldn’t it be simpler if Webmail would flag the bad ones at the initial send of the email. Perhaps there is software that will go through the list and find the bad ones. Any SW you know of?

You are describing the two levels of "invalid" that Shaw's mail-server software is currently doing:

1. invalid domain
2. invalid "@shaw.ca" ID

As regards your example of badfe11ow@telus.net, you are saying that shaw web mail actually sends it to the Telus mail server and you get an NDR back.  But what about the good email addresses on the list, does it send the email to the other good addresses on the list too?

You are correct.

Shaw's mail-server collates all the "@telus.net" IDs on your list as one "batch", and makes one connection to the Telus mail-server, and tries, one at a time, to complete delivery to each ID within the "batch".

Any mail-server has separate "queues" for each destination, e.g., one queue for messages to "@telus.net" IDs, one queue for messages to "@gmail.com" IDs, and one queue for messages to "@sasktel.net", and so on.  Thus, when the mail-server successfully opens a connection to the Telus mail-server, it processes all the messages in its "Telus" queue.  If the mail-server cannot connect to the Telus mail-server, it will switch to the queue for Gmail, and try to connect & deliver those messages.

From what I understand, Shaw Webmail wouldn't send it to anyone on the list, if just one is bad. 

Which level of "bad" is that one ID? As I wrote, above, the first level of "invalid" causes NO delivery to ANY ID on the list.

And what about mail servers other than Telus, are they all required to send an NDR back?

I would have to do some research, searching on "RFC822" (and its successors) to see if it is an absolute REQUIREMENT that a mail-server MUST send a "NDR".  But, I suspect that the short answer is "yes".

In essence, I understand from you that Shaw’s mail servers have recently changed to this non NDR report system.

Shaw's mail-servers handle the first-level (unknown domain) and the second-level (unknown Shaw ID), and send one type of "NDR" to you. The remote mail-servers do send a different form of "NDR" to you.

I have no evidence to support your "recently changed" conjecture.

It presents an new challenge and I am searching for a work-around.

There is no work-around, as long as you maintain the mailing-list. There are various "list-management" software packages that you can use, e.g., the open-source MAILMAN, the commercial LISTSERV software, and more.  The list of IDs is stored within their system, not by you, and those systems attempt to automatically handle each "NDR".  Unfortunately, there is no standard for the format of a "NDR". This means that sometimes, the software passes the NDR to you, as the list-owner, when it "gives up" on its attempt to recognize an incoming message as being a NDR.

Sending to an invalid "@shaw.ca" ID gives you immediate feedback. None of your recipients get your message.

Sending to an ID in an invalid (or "expired") domain is your problem, and you get immediate feedback from Shaw's mail-server when you try. None of your recipients get your message.

Each domain-name is valid for some length of time. Example:

Important Dates for domain "Google.com" are:

Registered On:1997-09-15

Updated On: 2019-09-09

Expires On: 2028-09-13

So, if Google were not to pay the fee to "renew" the registration of the name "google.com" before 2028-09-13, Shaw's mail-server would report "invalid domain", because the registration would have expired.  Such a failure to "renew" would certainly make the TV news, when all GMail customers on the planet are completely cut-off from their INBOX. Not only TV news, but all social-media and web-sites.

Thanks for any suggestions.

You're welcome. Handling "bounced" E-mail is a pain, but it is your responsibility as the "list-owner" of an "ad hoc" mailing-list.