Sender-dependent transport maps

TimmyT

Hello all!

First off, really enjoying the mailcow project!

I am running into the following problem:

Microsoft keeps blocking my dedicated ip because the volume to their email servers is too low.
To remedy this, i made transport maps to relay all email to microsoft services (hotmail.com, live.com ect) though mailgun with user account relay@domain1.com.

This works like a charm untill i add another domain2.com and dmarc rears it’s ugly head.

Because all email (to microsoft) is send through domain1.com dmarc fails for domain2.com (DKIM is not valid).

My questions:

is there a way to set up sender dependant transport maps?
is there a way to set up Sender-dependent transports to only transport email to microsoft services?
Is there another smtp service that can handle multiple domains with a single smtp account?

Any help or tips to circumvent the microsoft ip bans are also welcome.

Kind regards,

Tim

esackbauer

Strange, I also send low volume from my static IP and have no problems to send to Microsoft. Maybe its the TLD that you are using.

TimmyT

esackbauer

Hi Esackbauer,

Thank you for your reponse, glad to hear you don’t have any problems with microsoft!
Unfortunally my static ip gets blocked after around half a year.
Mitigation can take up to two weeks, wich is simply too long a wait for my needs.

The TLD’s that i am using are both .com and .nl.

Transport maps allow me to bypas my ipban using a smtp relay.
Unfortunally i have to choose between:

sending all mail through a smtp relay on a per domain basis (sender dependant transport) Or
sending only mail to microsoft services using a mail relay (transport maps). Unfortunally in this scenario i can’t sign the mail with a DKIM belonging to domain2 when using the relay for domain1, failing DMARC checks.

esackbauer

Can you please elaborate what exactly is failing with DMARC checks.
And how your DNS records for SPF, DMARC and DKIM are done.

esackbauer

Another thing to consider: I was hosting the DNS of one of my domains on Namecheap FreeDNS.
One domain I sent to was blocking my SMTP connection. Their postmaster said : "We block domains which are registered or DNS hosted on “free” servers, as most spam comes frome there."
I changed the DNS for the domain back to my regristrars DNS and everything was back to normal.

mbh

hi,
as i said in my post, we are facing same issue.
for mailcow instance hosting only one domain name, we using routing function
destination, next hop, account, pass
but for mailcow instance hosting several domain name, we should be able to route using destination, source domain, to select account used to send the mail…
Is it possible to achieve this using custom_transport.pcre or may postfix sender_dependent_relay_maps ?

Mehdi

esackbauer

That was not my issue, and the guy did not provide the information I requested. But as you are managing multiple mailcow servers which seems to be a commercial interest, you should consider paid support for mailcow. That might also be the reason why so far noone answered your original posting…

maybl8

Not sure if it would help your situation but I use sendgrid for outgoing mail.
[https://sendgrid.com/pricing/]
[https://docs.mailcow.email/manual-guides/Postfix/u_e-postfix-relayhost/]