Skip to main content

email server - Best Practices for preventing you from looking like a spammer




I'd like to feel more confident setting up mail for my clients with regards to false positives. Here's what I know:





  1. SPF records are good, but not every spam filter service/software (SFSS) uses them.


  2. reverse DNS (PTR) records are pretty much a necessity.


  3. Open relays are bad.



    (Here's "other tips" I've read):


  4. the reverse lookup of the IP address of your mail server should resolve to the domain that you're sending mail out from.


  5. your server should say HELO FQDN.of.your.mail.server.com when speaking to other mail servers.


  6. the A host records in MX records should be (or resolve to to the IP address) your FQDN.of.your.mail.server.com





Feel pretty good about 1 and 3. Here's where I'd like some clarification/suggestions:



2 and 4: I did alot of digging and this seems to be incorrect as most spam-filters are looking for a PTR in general and one that's not generically-assigned by the ISP; it doesn't appear that the domain you send mail out as has anything to do with this (i.e. if you owned two domains you used for mail, you'd need to send out from two IP addresses with PTRs for each?)




  1. This makes sense, but does it care what that FQDN resolves to? Should it resolve to the IP address that's currently sending said HELO?


  2. Again, another one from various Google searches; don't see how this would work if you used Postini as your gateway service (or any other smarthost for that matter).





And what about sending on behalf of another domain that you're not authoritative for? I have some clients (some.branchdomain.tld) that are required to send mail out as @some.corporatedomain.tld, even though said corporate HQ won't setup a relay/smarthost for them to use. corporatedomain.tld can create SPF records to show that some.branchdomain.tld is allowed to send mail, but would that still be considering "spoofing", especially if said SFSS doesn't check SPF records? Should I be concerned about this?


Answer



I can vouch for #2 (reverse PTR) being important, but not #4 (mail server domain matching "from"). We set up mail servers all the time, and most mail hosts don't really even care about #2.



The main thorn is always AOL, and they list standards you can check off.


Comments

Post a Comment

Popular posts from this blog

linux - iDRAC6 Virtual Media native library cannot be loaded

When attempting to mount Virtual Media on a iDRAC6 IP KVM session I get the following error: I'm using Ubuntu 9.04 and: $ javaws -version Java(TM) Web Start 1.6.0_16 $ uname -a Linux aud22419-linux 2.6.28-15-generic #51-Ubuntu SMP Mon Aug 31 13:39:06 UTC 2009 x86_64 GNU/Linux $ firefox -version Mozilla Firefox 3.0.14, Copyright (c) 1998 - 2009 mozilla.org On Windows + IE it (unsurprisingly) works. I've just gotten off the phone with the Dell tech support and I was told it is known to work on Linux + Firefox, albeit Ubuntu is not supported (by Dell, that is). Has anyone out there managed to mount virtual media in the same scenario?
Post a Comment
Read more

hp proliant - Smart Array P822 with HBA Mode?

We get an HP DL360 G8 with an Smart Array P822 controller. On that controller will come a HP StorageWorks D2700 . Does anybody know, that it is possible to run the Smart Array P822 in HBA mode? I found only information about the P410i, who can run HBA. If this is not supported, what you think about the LSI 9207-8e controller? Will this fit good in that setup? The Hardware we get is used but all original from HP. The StorageWorks has 25 x 900 GB SAS 10K disks. Because the disks are not new I would like to use only 22 for raid6, and the rest for spare (I need to see if the disk count is optimal or not for zfs). It would be nice if I'm not stick to SAS in future. As OS I would like to install debian stretch with zfs 0.71 as file system and software raid. I have see that hp has an page for debian to. I would like to use hba mode because it is recommend, that zfs know at most as possible about the disk, and I'm independent from the raid controller. For us zfs have many benefits,
Post a Comment
Read more

apache 2.2 - Server Potentially Compromised -- c99madshell

So, low and behold, a legacy site we've been hosting for a client had a version of FCKEditor that allowed someone to upload the dreaded c99madshell exploit onto our web host. I'm not a big security buff -- frankly I'm just a dev currently responsible for S/A duties due to a loss of personnel. Accordingly, I'd love any help you server-faulters could provide in assessing the damage from the exploit. To give you a bit of information: The file was uploaded into a directory within the webroot, "/_img/fck_uploads/File/". The Apache user and group are restricted such that they can't log in and don't have permissions outside of the directory from which we serve sites. All the files had 770 permissions (user rwx, group rwx, other none) -- something I wanted to fix but was told to hold off on as it wasn't "high priority" (hopefully this changes that). So it seems the hackers could've easily executed the script. Now I wasn't able
Post a Comment
Read more