Migrating mail servers from exim to OpenSMTPD (smtpd) is fun and useful https://www.undeadly.org/cgi?action=article;sid=20260516064650 #openbsd #opensmtpd #smtpd #exim #email #smtp #mail #spam #antispam #greylisting #greytrapping #mailmigration

If you are a #postfix user and think what is described in this HOWTO http://www.postfix.org/ADDRESS_VERIFICATION_README.html[1] is useful, I can tell you:

IT IS NOT.

Longer version: https://nxdomain.no/~peter/twenty-plus_years_on_smtp_callbacks_are_still_pointless.html

[1] a more appropriate title would be "Further punishing joejob targets HOWTO"

#smtp #postfix #smtpcallbacks #joejobs #greytrapping

System Administration: Week 8: E-Mail, Part III

In this video, we look at ways to combat Spam. In the process, we learn about email headers, the Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting and Conformance (DMARC). SMTP doesn't seem quite so simple any more...

https://youtu.be/KwCmv3GHGfc

#sysadmin #devops #sre #smtp

System Administration: Week 8: E-Mail, Part II

In this video, we observe the incoming mail on our MTA, look at how STARTTLS can help protect information in transit, how MTA-STS can help defeat a MitM performing a STARTTLS-stripping attack, and how DANE can be used to verify the authenticity of the mail server's certificate.

https://youtu.be/RgEiAOKv640

#sysadmin #devops #sre #smtp

System Administration: Week 8: E-Mail, Part I

In this video, we begin our discussion of E-Mail by looking at the components of the larger mail system (the Mail User Agent, the Mail Transfer Agent, the Mail Delivery Agent, an Access Agent), observing the packets involved in a simple SMTP exchange, and track an email from one system to the other.

https://youtu.be/Ai8rjqelwsI

#sysadmin #devops #sre #smtp

And finally, #SMTP. Looking at the Top 1M Domains' MX records, over 52% are IPv4-only; 45% fully dual-stack, and another 2% or so having at least one MX record with an IPv6 address.

But there are also large MX service providers who have IPv6 addresses on some MX records *and then don't accept traffic on those IPv6 addresses*, and large mail service providers like Yahoo, GoDaddy, and Namecheap (to name just a few) are completely IPv4-only.

#ipv6

Alt...

Total | % of MX records All MX IPv4 only 334,696 52.03 All MX IPv6 only 74 0.01 All MX dual-stack 288,849 44.91 At least one MX dual-stack 301,273 46.84 At least one MX IPv4-only 347,119 53.96 At least one MX IPv6-only 271 0.04 Only IPv4-only and IPv6-only MXs 89 0.01 Dual-stack with at least one IPv4-only MX 12,334 1.92 Dual-stack with at least one IPv6-only MX 108 0.01 Dual-stack + IPv4-only + IPv6-only MX 18 0.002 Dual-stack + only IPv4-only MX 12,316 1.91 Dual-stack + only IPv6-only MX 90 0.01 At least one MX IPv6 enabled (dual-stack or IPv6-only) 301,436 46.86