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Questions tagged [e-mailrelay]

40 questions
7
votes
2 answers

Why and how would I transmit emails via several Mail Transfer Agents?

I read in some Mail-Relay explanation that emails can be delivered from the sender's MTA to the recipient's MTA via more MTAs. How does it work (I thought, the sender's MTA simply determines the recipient's MTA's IP address by using DNS and directly…
user973109
5
votes
2 answers

What is difference between using smtp vs relay transport type in postfix?

I am trying to setup MTA which should submit different intranet mail gateways based on the recipient's domain. For that I thinks transport_maps in postfix should be setup for selective domains; if recipient domain is not matched with any line in…
SUNITA GUPTA
  • 215
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2
votes
1 answer

What difference does it make to implement a feature as policy service vs as milter in Postfix?

I am trying to implement MTA using Postfix. I am struck at how to implement standard services like SPF, DKIM etc. as well as some custom services. They can either be implemented as policy delegation service and called by check_policy_service or as…
SUNITA GUPTA
  • 215
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2
votes
2 answers

How to restrict based on combined usage of sender email and client ip address in postfix?

I have a MTA (postfix) with sasl implemented. I want that for a subset of users I can map their email address to a particular range of ips (separate for each email user). If a user tries to send email from outside his individual range the attempts…
SUNITA GUPTA
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2
votes
1 answer

Long established installation of postfix has become an open relay; how can I figure out how and stop it?

This server system has been serving email services since Red Hat v 1.1 (circa 1997 I think) and now is on Fedora Core 37; through many hardware and OS updates along the way it has been kept current. And, we chose postfix and dovecot early on, and…
Richard T
  • 1,332
1
vote
1 answer

Postfix content filter service recognizing it as relay

After about 30 hours of almost beating my head to the walls I had to come to the conclusion, it's better if I write to people who might be more well-versed in this topic. I have a Digitalocean server using Ubuntu 22. Yes I know Digitalocean does not…
FireyFly
  • 21
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1
vote
0 answers

How to configure Debian Exim to deliver through a relay only if a remote server rejects with certain messages (e.g., "_is_blocked.")

Using exim4 on Debian, how do I configure exim to attempt redelivery if I get a reject like: 553 5.3.0 alph747 DNSBL:RBL 521_is_blocked ... So, periodically my email server makes it onto a spamhaus list that spamhaus says "don't use…
chris
  • 11
1
vote
1 answer

How can I deliver incoming mail based on recipient domain with Postfix?

I have been digging for an answer to my current problem for several weeks now, so I am asking here in hopes someone can shed some light or point me in the right direction. I am attempting to configure Postfix such that: Inbound mail for…
user10709800
  • 13
1
vote
1 answer

Can I have more than one public keys saved in one selector for dkim?

The question is easy to understand, but it might be confusing. I understand that I can host multiple selectors for a DKIM record, but just out of curiosity, can I have multiple keys per selector in a DKIM TXT record?
SUNITA GUPTA
  • 215
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1
vote
1 answer

Why is it advised to disable relayhost when hosting mail server behind firewall?

I am trying to setup an MTA. While reading documentation I came across "Standard Configuration" for Running Postfix behind a firewall. I am confused on this part: IMPORTANT: do not specify a relayhost in main.cf. Why is it so?
SUNITA GUPTA
  • 215
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1
vote
2 answers

Can I log when the message arrival rate exceeds the message delivery rate in postfix?

I am trying to implement a MTA, on reading documentation of the postfix I found a parameter 'in_flow_delay' whose description in sort says 'Time to pause before accepting a new message, when the message arrival rate exceeds the message delivery…
Ayush Gupta
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1
vote
0 answers

What are typically the headers which I should oversign?

I am trying to setup MTA using Postfix and using opendkim for dkim signing. When I went through opemdkim documentation it have a field which is named 'OversignHeaders' document describes it as: "Specifies a set of header fields that should be…
Ayush Gupta
  • 57
  • 6
1
vote
0 answers

Unable to send emails from Postfix via Gmail (connect to smtp.google.com: Connection timed out)

I want to configure a Ubuntu Linode VPS to send log information from Fail2Ban, Apache ModSecurity and other monitoring tools to my email address. However, I don't want to configure a whole email sever: instead, I want to leverage Gmail as a relay…
LeperAffinity666
  • 111
1
vote
0 answers

How to prevent outgoing mails in postfix (or a mailcow instance)?

I want to use mailcow as an isolated mail server, so it's not supposed to send mails to the outside. The goal is to allow open registration on the mail server, and users should be able to communicate with each other - but I don't want to annoy the…
missytake
  • 11
1
vote
2 answers

How can I use E-Mailrelay to implement DKIM?

I am trying to add DKIM to an existing windows server which is currently using IIS SMTP for outgoing mail. It seems like this could be done by using E-Mailrelay. Unfortunately I could not find any reference on how exactly to configure DKIM in…
Adrian Grigore
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1
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