Issues with Microsoft send and receive

Hi everyone, been running a MIAB for 5 years now ( boy does time fly), I have a problem I keep hitting recently. Bill gates customers send me an email and it takes sometimes all day for me to receive them.

The sender gets a this basically.
Microsoft just returned it as “Undeliverable”

Remote Server returned '550 5.4.300 Message expired → 450 4.2.0

Recipient address rejected: Greylisted,

When I send my own outlook account an email or I send one to myself it works fine sometimes taking 30 seconds or so. Someone with a corporate outlook account it takes 6 hours to get to me. I have everything setup decent, I use mail-tester com and am getting a 95% score. DMARC AND SPF is setup. I also went to etc / greylist and added and to the whitelist_clients.

I am running an older version that I have updated in the status checks this is what I get, I haven’t done the full upgrade because I am a little scared to venture in to broken server world.

System software is up to date.

A new version of Mail-in-a-Box is available. You are running version v0.30. The latest version is v56. For upgrade instructions, see

Thanks everyone.

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I am also running an old version v0.29, and had exactly the same issue (and error message) today with emails sent to me through microsofts service.
The strange thing is, that I received emails from the same addresses just two days ago, with no problem (maybe some lag).
I had to give them an email at another provider (protonmail) because adding the senders host IP to my whitelist didn’t help.
This is the first time something like this happened, and the server was created 6 years ago.

Could it be caused by something outdated in the old version?
I would experiment with a new droplet and a fresh install of miab, but I just don’t have the time now.

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I have been thinking it could be an outdated TLS 1.0 vs. TLS 1.2 or something stupid like that, Today I received email from a lot of MSFT email clients, but Thursday it took about 8 hours to get emails sent from a corporate outlook account. My emails are getting there in 5 minutes or less to them with no issues. I do wish there was a tool like to help diagnose this.

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Same problem here.

In January I had a send problem because my box is in Linode, and Microsoft blocked most of their IPs.

It is now resolved, but now I have the greylist problem you are describing.


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Jeremy what version are you running?

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I’m running v0.30

I edited the whitelist file for postgrey yesterday, following the advice of this link.

Now I can receive evertything from, but I’m still having problems with other senders.

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Time to update these boxes before problems more severe than Microsoft arrive.

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Thanks for your feedback!
I’d feel safer with an up-to-date system but was afraid of jumping into the process.

I was thinking that the least risky way to go would be to create a completely new install on another server, then move the mailboxes, starting with the least important domain…

@ jtrench
I wasn’t aware of the blacklisting problem with Linode, I thought that was a DigitalOcean problem only.
My current mailinabox is running on DO and it was blacklisted for years…it now seems to be clean though.

I have attempted to upgrade using the backups months ago; it failed. deleted the linode and made another attempt, moved on to other tasks. I do host a lot of domains on this box, but I have been thinking of starting from scratch. Possibly a migration plan is best. I would guess that at this point openletter is suggesting it could be linked to the older software, but the risks of running an out of date box is worse.