Does the rejection message tell you which blacklist is being used? Have you contacted them to complain?
A lot of the time the rejection message gives you a URL to click on - and sometimes that URL leads to a mechanism to complain or tells you how to do so.
I understand that you have pursued this at the Librem One end but there’s only so much that they can do.
Groups IO doesn’t respond.
Grious IO bounces don’t point to a blacklist, they use the 4.4.1 timed out error.
Bounces from other email providers which began bouncing at the same time used the 5.5.4 blacklist error.
Groups io is obviously hiding behind sysadmin double-speak.
It is possible that groups.io have implemented the blacklist at the firewall level in some cases. So that means that the sending SMTP server (Purism) cannot communicate with the groups.io receiving SMTP server at all, so the sending SMTP server (i.e. Purism, not groups.io) gets a “connection timed out” and reports that to you as a 4.4.1, but because “connection timed out” is a transient error, Purism will keep trying for X days (where X may be 5, depending on Purism configuration), before reporting the failure to you.
More polite receiving SMTP server behaviour is to reject with a 5xx (permanent) error, so that the email fails immediately and the sender stops trying.
On my own receiving SMTP server I would only use the firewall “nuclear option” when under sustained attack i.e. ongoing frequent bogus SMTP sessions from the same IP address, rather than just annoying spammers or alleged spammers.
When I try to connect to the groups.io receiving SMTP servers, I can successfully connect and communicate. Only Purism can conduct the same test from their sending SMTP server (e.g. 192.241.223.110).
I have two work arounds, log in to groups.io. Post from their web page and have an alternate identity with gmail. Which meant subscribing twice to each group I’m a member of, and for the groups I own, making my alternate identity a co-owner.
Which means I receive double-tapped emails in Thunderbird. So I file messages from one account, but delete the others.
Two weeks ago, Joao from the support team told me, librem.one will be switching IP addresses, so they won’t be blocked anymore. I don’t know if they did, but mails get rejected from gmx still.
EDIT: just found an old posting mentioning the IP address of mx1librem.one. The IP address hasn’t changed, it still is
192.241.223.110.
Technically, mx1.librem.one and mx2.librem.one are the domain names for incoming email to librem.one and need bear no relation to the IP address(es) (domain name(s)) for outgoing email. Hence you need to see the IP address that is listed by gmx in their rejection message. (It wouldn’t surprise me if it had not changed however. Let’s tag him in: @joao.azevedo )
I can only reiterate: I have found gmx in the past to be unhelpful and uncooperative in resolving problems like this.
FYI: Groups.io had been working for a week, for both receive and transmit it stopped again this morning for transmit. Kept my gmail subscriptions active so I’m going to the fall back position there.
Based on their spf record there are two allowed IP’s for sending.
v=spf1 ip4:192.241.223.110 ip4:162.243.130.145 -all
I haven’t checked for historical values, but this would be the record to check for valid sending IP’s
I’ve just been informed by @joao.azevedo that the librem.one system administors have worked on the problem last weekend. Indeed, gmx now accepts emails from the librem.one domain! My test mail ended up (as predicted by Joao) in the spam folder of the receiving mailbox, but at least it reached it’s addressee.
Congratulations! Now all you have to do is train your client not to file them there.