Dear all, I just deployed Mailcow on my self-hosted server and am encountering an issue I can't figure out. 1. When I test my server's configuration using the Mail Tester website, I get a score of 10/10: 2. My server exchanges emails without any issues in both directions (sending and receiving) with Microsoft, Gmail, and Proton servers, which are known for being strict. 3. My IP address does not appear on any blocklists. This seems to indicate that my server is properly configured and that nothing is preventing it from functioning correctly. However, I’m having an issue with my ISP’s mail servers (Free.fr, a major provider in France): * Receiving works. I receive emails sent from Free.fr’s webmail in Mailcow’s webmail. * Sending doesn’t work. When I send an email to a `@free.fr` address from my Mailcow webmail, I never receive it in the Free.fr webmail. In the logs of the `postfix-mailcow` container, I see lots of messages like this one: ```log Apr 16 22:26:50 48ec1526b15e postfix/qmgr[369]: 7DB0B5C902C: from=, size=141685, nrcpt=1 (queue active) Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx1.free.fr[212.27.48.7] while receiving the initial server greeting Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx1.free.fr[212.27.48.6] while receiving the initial server greeting Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx2.free.fr[212.27.42.58] while receiving the initial server greeting Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: to=, relay=mx2.free.fr[212.27.42.59]:25, delay=201000, delays=201000/0.12/0.1/0, dsn=4.4.2, status=deferred (lost connection with mx2.free.fr[212.27.42.59] while receiving the initial server greeting) ``` Do you have any idea what might be wrong and what I could do to identify the cause of the problem? Thanks in advance for yout help, Sébastien

> @"sdinot"#p31969 My IP address does not appear on any blocklists. Well, it is listed at Spamhaus... [upl-image-preview uuid=93a82e1f-7d94-4e94-b747-133feaf8f18e url=https://community.mailcow.email/assets/files/2026-04-17/1776406656-268439-image.png alt={TEXT?}] https://mxtoolbox.com/SuperTool.aspx?&action=blacklist:82.64.74.177&run=toolpage#

lost connection with ... while receiving the initial server greeting

sdinot

Dear all,

I just deployed Mailcow on my self-hosted server and am encountering an issue I can’t figure out.

When I test my server’s configuration using the Mail Tester website, I get a score of 10/10: https://www.mail-tester.com/test-xrefcszk8
My server exchanges emails without any issues in both directions (sending and receiving) with Microsoft, Gmail, and Proton servers, which are known for being strict.
My IP address does not appear on any blocklists.

This seems to indicate that my server is properly configured and that nothing is preventing it from functioning correctly.

However, I’m having an issue with my ISP’s mail servers (Free.fr, a major provider in France):

Receiving works. I receive emails sent from Free.fr’s webmail in Mailcow’s webmail.
Sending doesn’t work. When I send an email to a @free.fr address from my Mailcow webmail, I never receive it in the Free.fr webmail. In the logs of the postfix-mailcow container, I see lots of messages like this one:

Apr 16 22:26:50 48ec1526b15e postfix/qmgr[369]: 7DB0B5C902C: from=<zebulon@palabritudes.net>, size=141685, nrcpt=1 (queue active)
Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx1.free.fr[212.27.48.7] while receiving the initial server greeting
Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx1.free.fr[212.27.48.6] while receiving the initial server greeting
Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: lost connection with mx2.free.fr[212.27.42.58] while receiving the initial server greeting
Apr 16 22:26:50 48ec1526b15e postfix/smtp[7412]: 7DB0B5C902C: to=<sebastien.dinot@free.fr>, relay=mx2.free.fr[212.27.42.59]:25, delay=201000, delays=201000/0.12/0.1/0, dsn=4.4.2, status=deferred (lost connection with mx2.free.fr[212.27.42.59] while receiving the initial server greeting)

Do you have any idea what might be wrong and what I could do to identify the cause of the problem?

Thanks in advance for yout help,

Sébastien

DocFraggle

sdinot My IP address does not appear on any blocklists.

Well, it is listed at Spamhaus…

https://mxtoolbox.com/SuperTool.aspx?&action=blacklist:82.64.74.177&run=toolpage#

sdinot

Hi @DocFraggle,

Thanks for this trail. To be more precise, my server’s IP address was listed on Spamhaus. I have requested that it be removed from the list and Spamhaus did it:

But maybe you are right. My messages are not delivered to Free.fr simply because that ISP’s servers update their blocked address list less frequently than Microsoft, Gmail, and Proton.

If that is the case, I hope everything will be back to normal in a few days.

In the meantime, it is frustrating—I still cannot send legitimate emails to @free.fr addresses, but I am already receiving spam that Rspamd is not blocking. :/

DocFraggle

sdinot To be more precise, my server’s IP address was listed on Spamhaus

No, it actually IS (still) listed right now. You can check yourself

https://check.spamhaus.org/results?query=82.64.74.177

Your screenshot shows the CSS blocklist, I guess this is another thing

tobiaseigen

I’ve been down this rabbit hole before.. it is frustrating and you feel so powerless!

Don’t know what you are using your mailcow for but if you are using it to send bulk email you might consider switching to mailgun or some other transactional email provider. You will have better luck and not have to worry about your IP being blocklisted which will continue to happen.

Email is hard!

sdinot

tobiaseigen if you are using it to send bulk email you might consider switching to mailgun or some other transactional email provider

Not at all, it’s just for personal use.

I self-host most of my services, so it seems only natural to host the email system as well.

tobiaseigen Email is hard!

I know. 🙁

sdinot

DocFraggle No, it actually IS (still) listed right now. You can check yourself

Damn! 😥 I just submitted a removal request.

tobiaseigen

🤗

sdinot

@DocFraggle, my removal request has been approved by Spamhaus, and my ISP’s mail servers now accept emails sent from my self-hosted mail server.

Thank you very much for pointing out the block that I had missed.