Greylist not working with hosted accounts

RSW

New Member
Jan 27, 2022
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The email filtering has been working fine for ages, however now lots of our customers have moved to online hosting of email services with Google or MS we are finding that to many emails are being forever greylisted. The domain for the customer is in the whitelist in who objects but I can see the customers being greylisted in the tracking as the emails are comming from different ip's each time.

Is there a way to deal with this or just turn of the grey listing?

Thanks
RSW
 

mira

Proxmox Staff Member
Staff member
Aug 1, 2018
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You could change the Netmask for Greylisting IPv4 in Configuration -> Mail Proxy -> Options to whitelist a bigger subnet once it goes through.
And there's also the possibility of disabling greylisting via the SMTP Whitelist (Configuration -> Mail Proxy -> Whitelist) instead of disabling it globally.
 

RSW

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Jan 27, 2022
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Does the Mail Proxy Whitelist use the email domain or the sending server domain to bypass greylisting?
IE. I don't want to put Google here I want to put my customers domain
 

RSW

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Jan 27, 2022
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Thanks for the help I will try the whitelist in Mail Proxy, however I think this is something that needs to be looked at going forward as more people move to online email services
 

mira

Proxmox Staff Member
Staff member
Aug 1, 2018
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As mentioned in my first reply. In those cases you can change the netmask for greylisting, for example to allow a /20 instead of /24. In some cases this is enough to cover different sending IPs for one mail provider.
 

RSW

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Jan 27, 2022
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But I don't want to white list all Google or MS email servers by IP as that is where lots of spam comes from.
I only want to white list people or domains I get emails from regularly
However if these people use Google or MS then the IP is always changing and they get caught in a greylist loop
 

mira

Proxmox Staff Member
Staff member
Aug 1, 2018
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Greylisting works by saving a tuple of Sender IP, Sender Mail Address and Recipient Mail Address to check against.
If no entry is available for this, it will greylist it by sending a temporary failure. If the mail is sent again a few minutes later, it will go through and that tuple will be whitelisted for 30 days.

But it's not actually the Sender IP, but rather a /24 subnet (by default) that is saved in the tuple. Which means when changing the netmask for greylisting, this subnet will also change. If you then allow a /20 instead of the /24, any mail that's sent from the same sender, but with a different IP still in that subnet, will go through just fine as it is still whitelisted.

I hope that clarifies it, and why changing the netmask can help improve this without manually whitelisting any IP ranges.
 

RSW

New Member
Jan 27, 2022
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Thanks for the detail never seen this before that it is combined from the 3 items

Cheers
 

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