Mailing listsDeliverabilityMailman 3 In service since July 2026

The medical biologists' union replaces lists that Gmail and Outlook were starting to block

Its lists ran on Ezmlm, OVH's mailing list system. As the big mail providers brought in new security rules, its mail was being blocked or slowed down, and it was becoming critical. We moved the lists to Mailman 3, on a server dedicated to the union.

By Thibaut GalbaOctober 20266 min read

Mail serverMedical biologists' union

In service

Replaces: Ezmlm, OVH's mailing lists
Hosted: In France, in the union's name
In service: Since July 2026
Maintenance: Handled by WebWize

Mail provider checks What Gmail and Outlook check

SPFaligned
DKIMaligned
DMARCaligned
Mail-tester test10/10
Third-party sending servicenone

mailing lists, created and configured on 8 July 2026

10/10 on the mail-tester deliverability test

0 blacklists out of the 49 tested

12 lists created on Mailman 3

Readings taken on the server from June to September 2026.

ClientMedical biologists' union SectorHealthcare, sensitive data BeforeEzmlm, at OVH ServiceMigration, then hosting and maintenance WebWize teamThibaut Galba ToolsMailman 3, Postorius, Postfix, OpenDKIM

An ageing system, blocked more and more by the mail providers

Gmail, Outlook, Yahoo and Orange check more and more strictly where each message comes from. An old list system like Ezmlm struggles to comply with these new rules. The union's mail was being blocked or slowed down, and it was starting to become critical for its communications.

Before

Ezmlmthe OVH lists

Mail providersGmail, Outlook…

Sendingblocked or slowed down

What the mail providers now check

SPF
The domain says which servers are allowed to send in its name.
DKIM
Each message carries a signature, which proves it was not changed on the way.
DMARC
The displayed sender must match this evidence. If not, the message goes to spam or is refused.

The client

Medical biologists' union

Healthcare sectorSensitive data

It needed

messages that pass the checks of Gmail, Outlook, Yahoo and Orange
to bring across every Ezmlm subscriber
no third-party sending service, because union membership is sensitive data (GDPR, Article 9)
a server in the union's name, which it can take over

A move to Mailman 3, carried out in stages

The data is sensitive. So we ruled out online sending services such as Brevo or Mailjet, and a shared server. The union has its own server, in France.

SenderA member

writes to the list from their usual mailbox.

Mailman 3The list

publishes a board member's message, or sends it to a moderator for one-click approval.

Postfix · OpenDKIMThe dedicated server

rewrites the sender in the list's name, signs the message and sends it.

SPF · DKIM · DMARCThe members

Gmail, Outlook, Yahoo or Orange check where it comes from, then deliver.

A list adds a footer, which breaks the original signature. So Mailman 3 rewrites the sender in the list's name for every message (Munge From and unconditional DMARC mitigation settings), and the server signs in its place.

May 2026Scoping
A twelve-page deliverability audit, then the architecture agreed with the union.
18 June 2026Setting up the server
Postfix, Mailman 3, Postorius and OpenDKIM in one day, 10/10 on mail-tester.
22 June 2026Passing DMARC
Gmail goes from a failure to a pass, and files the message in the inbox.
8 July 2026Creating the twelve lists
In one day, on a baseline of settings approved by the union.
21 July 2026One-click moderation
Moderators approve a message from their mailbox.
Aug. and Sept. 2026Scaling up
A new server has no reputation. The union imports its members in stages.

What has changed since July 2026

BeforeSince July 2026

The list system

Ezmlm, the OVH mailing lists

Mailman 3 and its Postorius interface, on a dedicated server in France

Gmail, Outlook and the others

Mail blocked or slowed down more and more often

SPF, DKIM and DMARC aligned, 10/10 on mail-tester. Gmail did not delay a single message from 24 August to 16 September 2026

The server's reputation

not measured

Not listed on any of the 49 blacklists tested on 15 September 2026

Sending

not measured

Through Postfix, from the dedicated server, with no third-party sending service

Lost messages

not measured

None from 24 August to 16 September 2026, and no unsubscriptions

Before: Thibaut Galba's findings at the start of the project. Since: readings taken on the server from June to September 2026.

Excellente équipe ! Toujours à l'écoute et très réactive. Nous avons pu automatiser pas mal de nos process grâce à eux. Je vous les recommande chaudement.

General secretary
Medical biologists' union · Google review

The union runs its own mailings, and we monitor the server

Since 30 July 2026, the union has been importing its members itself. We monitor the server's reputation with Gmail using Google Postmaster Tools, its presence on blacklists and its access to Outlook, then we give the union our view.

In service sinceJuly 2026

Monitored and maintained by WebWize.

The union imports
It adds its members itself, in stages.
The sentinel measures
A reading every hour, and an alert if the light turns red.
A review every morning
It covers the previous day, from midnight to midnight.
Our view
Green, amber or red light, and a request to stop if needed.

29 July 2026

Outlook unblocked

Microsoft was refusing messages from a whole range of the host's addresses, not just the server. It lifted the block at our request.

15 Sept. 2026

Orange and Microsoft slow things down

On the first mailing to a large list, more than 95% of messages go out in under ten seconds. That same evening, we limit Postfix's connections to them.

16 Sept. 2026

A progress report delivered

Six pages for the union on how it went, the results by mail provider and the addresses that bounce.