Outgoing emails from Distribution List flagged as "Undeliverable"

[jeallen01]

Good afternoon (after a long absense!)

My ISP is virginmedia.com and I now appear to be on the M125 cable to premises system;p and  I routinely use MS Outlook 2019 as my email client on an quad-core HP Elitedesk G2 running W10 Pro on an SSD, & with 16Gb of RAM.

My problem is that I sometimes use an Outlook  Distrbution List which has around 30 or so recipients in it - and all of those receiving email addresses have been verified as being correct.

Nevertheless, when I use one of my gmail addresses to send stuff to that Distribution List, I occasionally, and immediately, get a few "Undeliverable" responses in my gmail Inbox. Addiionally, it now seems like 2 or 3 particular recipients with either gmail or btinternet addresses are the ones that appear to have this issue - they don't get the messages just after they are sent by me, but sometimes do appear to get them a few hours later!

OTOH, having discussed the issues with those relevant recipients, it appears that they aren't having problems with not getting emails from senders other than myself and thus are getting emails from the former.

Therefore I wonder if anyone else has (or had) similar issues and what, if anything, can be done to "fix" them?

Thanks in advance.

[jeallen01]

PS to my first post: should have mentioned that the EliteDesk G2 is connected to my ASUS Router and then to the Virgin cable router (in modem mode) by a 1Gb wired ethernet nework - no WiFi connections are involved!

[用心棒]

What reasons are given in the Undeliverable notices?

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[jeallen01]

Thx for the interest & the question:

These emails have "System Administrator" as the Sender and "Undeliverable: Hu3a Photography Group - useful tips on ePhotozine website" as the email subject.

The text of these emails typically looks like the following (but the intended recipients's actual email addresses have obviously been disguised!):

"Your message did not reach some or all of the intended recipients.

      Subject:     Hu3a Photography Group - useful tips on ePhotozine website

      Sent:  16/10/2022 12:41

The following recipient(s) cannot be reached:

      'Alan XXXX (mailto:alanXXXX@supanet.com)' on 16/10/2022 12:41

            Server error: '553 5.1.3  https://support.google.com/mail/answer/6596 g17-20020a05600c4ed100b003b4ac05a8a4sm16232595wmq.27 - gsmtp'

    'Ian WYYYY (w.i.WYYYY51@outlook.com.)' on 16/10/2022 12:41

            Server error: '553 5.1.3  https://support.google.com/mail/answer/6596 g17-20020a05600c4ed100b003b4ac05a8a4sm16232595wmq.27 - gsmtp' ""

Other similar messages related to recipients with BTinternet.com & gmail.com addresses.

The quoted support.google address gives some general "info" on what might be happening but I'm not sure what to make of that.

Therefore thanks in advance for any insights/guesses as to what is actually happening in cases like these!

[用心棒 · Accepted solution]

The 5.1.3 status indicates “Bad destination mailbox address syntax”. Are you able to email the recipients individually? If you are then you would need to ask the recipients to seek an explanation from there providers as to why the emails are not getting through

[jeallen01]

Thx and, all along, it's been my "feeling" that the problems lay at the recipients's ends bcause multiple other recipients of the same emails DID receive those emails. Therefore I will pass your reply to them and ask them to check with their ISPs.

However, one other vaguely possible cause of the issue did cross my mind: could the relatively large (?) number of recipients (around 30 or so) have caused a "glitch" due to some sort of "overload" at my sending end?

[jem101]

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@jeallen01 wrote:

Thx and, all along, it's been my "feeling" that the problems lay at the recipients's ends bcause multiple other recipients of the same emails DID receive those emails. Therefore I will pass your reply to them and ask them to check with their ISPs.

However, one other vaguely possible cause of the issue did cross my mind: could the relatively large (?) number of recipients (around 30 or so) have caused a "glitch" due to some sort of "overload" at my sending end?

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And you are probably right! An email distribution list has no meaning to an email delivery system, when you send an email to a DL, the client (Outlook 2019) has to ‘expand the list’ and send an individual email to each member. If you can send a single email to each recipient on it’s own, and they receive it, then the mail delivery system is fine.

It strikes me that the issue is with Outlook and the DL itself, personally I’d set a new distribution group up, add the users again (maybe test after adding a few, then add a few more and test again) and see if that works. If it does then blow the original DL away.

[jeallen01]

Thx for the comments.

So far, I have simply amended the DL by removing the "problematic" addressees and then adding them back in from my Outlook Contacts list, and then I'll wait to see what does/doesn't happen next time I use it to send out a Group message.

Frankly I can't be bothered to (as yet!) create a new DL "piece by piece" and test it as I go along because, half the time even the problematic recipients won't respond in "quick time" or then do any checks that I ask of them (& in one case, is frankly barely capable of understanding what I might ask of him, or doing it).

Therefore I'll have to see how this plays out over the next few weeks - But thanks for all the info & suggestions which have given me quite a lot of food for though on how to go about trying to fix the issue(s) that I have been encountering!