Setting up new mail server and avoiding spam filters

Question

So I'm attempting to setup a mail server on my web server using this guide: https://www.digitalocean.com/community/tutorials/how-to-configure-a-mail-server-using-postfix-dovecot-mysql-and-spamassassin

I've since completed it but after trying to go through the steps I am still getting caught in spam filters. Using mail-helper it shows that I'm still missing some errors which rates my emails at a 6.5/10 on their site.

Received-SPF: pass (google.com: domain of x@x.me designates 0.0.0.0 as permitted sender) client-ip=0.0.0.0;
Date: Tue, 31 May 2016 01:47:46 -0600
Subject: Tester
From: Me <me@website.me>
To: phlexplexico@gmail.com
Importance: Normal
MIME-Version: 1.0
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: base64
Message-Id: <20160531074749.5ACCC144672@website.me>

PHAgZGlyPSJsdHIiPkhleSB0aGVyZSEgTGV0J3Mgc2VlIGlmIHRoaXMgaXMgbm90IGJsb2NrZWQu
PC9wPgo=

I removed some info about my website as it is personal, but I know the DNS checks are correct and they all work. However, what mail-tester gives me an error about is certain headers, such as missing MIME-OLE and

Message only has text/html MIME parts
You should also include a text version of your message (text/plain)

So what am asking mainly is where can I edit my headers to include or remove X-MSMail-Priority from the headers, and how can I send a text version of the email via postfix/dovecot? I'm also just using the gmail app to send these emails through my account. Thanks in advance for the help!

score 2 · Accepted Answer · edited Oct 07 '21 at 07:34

In your question, you state:

I'm also just using the gmail app to send these emails through my account.

while in the header of the attached e-mail, I see:

Received: by website.me (Postfix, from userid 1000)

so, actually, you're sending such an e-mail via your local Postfix (...and not the GMAIL APP... whatever it is!).

Also:

So what am asking mainly is where can I edit my headers to include or remove X-MSMail-Priority from the headers

the answer is quite easy, as such an header (X-MSMail-Priority), exactly like any other X-whatever headers, are added by MUAs. In simple terms, it's the application that you have used to send above e-mail that added such header. So, to remove such header, you only need to "fix" such application.

Finally:

and how can I send a text version of the email via postfix/dovecot?

here you're referring to the complaints about the MIME parts. The reason for such a complaint is that your e-mail declares, in the headers:

MIME-Version: 1.0

so, basically, it say: "Hei! I'm a MIME 1.0 e-mail". Actually, it say that the message is compliant with RFC 2045.

Right after such a declaration, than, it say:

Content-Type: text/html; charset=utf-8

so, something like "Hei! here follow a text/html content....". And, actually, the content of the e-mail is not even an HTML! It's the string "Hey there! Let's see if this is not blocked" BASE64-encoded. In other words, the message is NOT compliant with the RFC 2045 above.

The mail-structure-check-service you've used, has noted such a mismatch and it correctly report this to you.

In the end: I strongly suggest you to carefully check the structure of the to-be-sent e-mails. Even more important, I really think that to send automatic e-mails, it's much, much better to use one of the readily-available libraries, that have been developed to correctly deal with problems you're experiencing (in PERL, for example, I like this; but there are plenty, for every programming language). By proceeding writing code by hand, from scratch, might result in a very hard path.

Setting up new mail server and avoiding spam filters

1 Answers1