Your best, easiest and most globally available tool: telnet At command prompt, type: telnet mail.mailserver.com 25 Type EHLO , and then press ENTER. Type AUTH LOGIN. The server responds with an encrypted prompt for your user name. Enter your user name encrypted in base 64. You can use one of several tools that are available … Read more
I discovered that the problem was that although we had SPF records set up for our domains, we did not have a DKIM record associated with our domain. In order to add a DKIM record in Google Apps, you need to do the following: Go to the Admin Console Click on “Google Apps” Click on … Read more
You’re looking at the wrong things. Those are the message headers. You should be looking at the SMTP envelope. (How the envelope is specified depends from how, exactly, your application is submitting mail to the mail system. On many systems the envelope is specified by command-line arguments to the mail submission utility program.) Depending from … Read more
In general, both are mail relays, and a mail relay is just a server that passes mail to another mail server, via SMTP, rather than a server that offers mailbox service to end users via POP3/IMAP/HTTP. A smarthost is a mail relay that is specialized to deal with outbound email. If you have a private … Read more
smtp_tls_security_level = encrypt or smtp_enforce_tls=yes For specific destinations you could use smtp_tls_policy_maps smtp_use_tls = yes and smtp_enforce_tls=yes are deprecated. With Postfix 2.3 and later use smtp_tls_security_level instead. Remember: Enforcing TLS encryption could cause mail delivery problems for SMTP host, that doesn’t have TLS configured. If server is used to deliver mails to only your internal … Read more
RFC 822 actually gives an example of this usage. It required (Section 4.4) that the Sender: header be present when it was used. A.2.7. Agent for member of a committee George’s secretary sends out a message which was authored jointly by all the members of a committee. Note that the name of the committee cannot … Read more
Update 2019: Conditional Greylisting is the best trade-off After having used greylisting on all mails for a long time on a busy mailserver, I stopped doing so. It delays ham mails unnecessarily. This is especially annoying for mails with account activation links. It creates severe problems with cloud mailers that you need to whitelist (details … Read more
If you have python lying around this will write the SMTP conversation to stdout. sudo python -m smtpd -n -c DebuggingServer localhost:25 http://docs.python.org/library/smtpd.html#debuggingserver-objects