Help troubleshooting email server, emails ending up in spam

I've had an email server running for about 6 months, this server was set up with the intention of only being for outbound notification emails for my other websites.
The email server is it's own separate machine.

So during this time frame everything went fine, emails arrived as they should and so forth. However, as of around December 1st (possibly earlier, I am not sure) I noticed that services like Gmail have been sending them to spam.

The SPF, DKIM, and DMARC all pass according to Gmail so I am at a loss there.

Let's say I have two servers, and the latter being the url of the mail server.

My DNS records look like this:

TYPE /       NAME      / VALUE
MX   /   /

TXT  /   / v=spf1 mx a -all

TXT  / mail._domainkey / v=DKIM1; k=rsa;p=LONGSTRINGHERE

TXT  /      _dmarc     / v=DMARC1; p=none; sp=none; rf=afrf; pct=100; ri=86400`

I'm using cloudflare so the root domain get's omitted from the NAME field but is still the same, so mail._domainkey and are the same here.

edit: pre-formatted text for readability.

I'm hoping that someone here has some tips on what I should look at to hopefully fix this. I'm at a bit of loss as this happened without me changing any configuration.


Is stuff you send or receive getting caught?

Have you checked your domain to see if its been getting caught as a spam domain?

The email server is outbound only, the messages being sent are being caught.
Checking the IP and domain against blacklists shows it not being listed anywhere.

Additionally, I know that SpamAssassin does not block emails from my server. For all I know it could be some weird Gmail-only thing.

has been pretty reliable for me if you need a resource.

I was having a problem with postfix not sending to Hotmail/Live accounts (ends up in spam) but Gmail and Yahoo would work fine. I never sorted it out, just switched over to fastmail because it just wasn't worth my time. For the record, Fastmail is an excellent option with some of the best security features I've seen in a while. You can set separate passwords for different programs/devices so that if you, say, lose your phone, you only disable access through that password and you don't have to reset the password on all your devices. It's pretty badass.

hmm, no blacklists at all.

Fastmail isn't really what I would be looking for if I gave up on this. I don't need a full-on personal email service since I only need outbound alerts (and for several domains/websites at once).

Pegasus Mail will do that relatively easy.

Better to fix your current configuration though. I had a similar issue a few years ago with one of my domains at work. Our .net would get caught in google spam but the .com would not. To settle the issue I called some number at google and got transferred about 10 times and finally talk to someone who said they'd queue it for a fix. About a month later the e-mails worked correctly.

Is this happening across several different gmail accounts? Did you create a fresh gmail account to test that one?

I have tried for several gmail accounts just now (mine and friends) with the same result.

Though now I actually just tested with an Outlook (hotmail) email and my server gave this back:

part_3 part_2
This is the mail system at host

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

: host[] said: 550 SC-001
    (BAY004-MC6F20) Unfortunately, messages from weren't sent.
    Please contact your Internet service provider since part of their network
    is on our block list. You can also refer your provider to (in reply to MAIL
    FROM command)

So I'm assuming I'm kinda screwed here and for some reason my hosting provider has their network blacklisted as a whole?
I only assume this because of the "contact your Internet service provider since part of their network is on our block list" message.

It could be possible the proxy cloud flare assigned you has been blacklisted in the past.

hmm, I don't think it the would be the issue. I was using Cloudflare for DNS only and no proxy.

So should I burn it to the ground? It doesn't seem like there is anything more I can do in this specific situation...

At this rate I might as well just use gmail accounts since at least that would work consistently (joking)

The problem is that this affects 5 websites I'm running so this is somewhat a big deal for me, I need to be able to get this working one way or another.

Edit: wow I actually get a 10/10 on was a waste of effort hehe...

Contact your hosting provider and raise the issue. I had that happen with my hoster, as a customers machine on the same /16 mine is went nuts after being compromised.
They were able to dispute it with gmail, hotmail (msn), gmx,, ... and since than I am again able to send e-mails from my domain(s).

The server, though passing everything, like yours - got just collaterally blocked

Do you have a Reverse PTR record set up or are using a Smart Host Relay from your ISP?

If not even you haven't been blacklisted publicly yet the IP Address your sending from will not be well liked or well trusted on the internet for email.

Any ISP should be able to get a PTR record setup fairly quickly though like anything DNS it could take a few days to propagate. Using a Smart Relay if your ISP has one may be quicker.

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Thats a good one! I should have thought of that, cuz I myself dismiss senders without a matching PTR ^^


Have a look at your mailserver with they test all the little things you need to take care of.

Okay, I've submitted a form and got my server unblocked for Hotmail/Outlook. Now it goes to spam rather than being blocked completely.

I had forgotten to do this for a while, but even so it had worked fine. I have had this set for a bit though so it shouldn't be the cause of the issue. I wouldn't know how to set up a smart relay.

I'll try contacting my hosting provider to see if they can do anything, the support is very sluggish.


I resorted to getting a new ip address, which I was trying to avoid due to how bad that looks.

It got my messages out of spam for Gmail at least but outlook blocks it, figures...

According to SNDS the new IP is also blacklisted, so it's most definitely the host and not something I did.

I have sent a whitelist requests to AOL and all that jazz, clearly this is a mess...

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I wouldn't bother trying to clean up the reputation of the IP, you just get more of the same problems in the future again. Can you change your hoster?

Various 'Webmail' providers have been cracking down a lot lately on this sort of thing making it very frustrating for some. I've had a few customers who've had issues sending email to them because of things like PTRs not being setup properly and therefore their mail not being trusted by the receiving server even though the mail itself is perfectly legitimate.

Don't even get me started on AOL and their policies lately...

A Smart Relay is a mail server your ISP provides for you to send mail through instead of sending it direct from your server. The logic being the ISPs relay server is far more trusted then your own because it has all the latest i's dotted and t's crossed to be compliant with the latest standards and therefore be liked by the mail servers your sending mail to. They are also usually included as part of your broadband package and therefore free of charge as long as you aren't abusing it with spam.