I have some clients for whom I manage hosting but I don't actually run the hosting servers. Most of the domains are together on one server/IP address (along with other domains that aren't mine).

One of my clients has started getting a bunch of her emails rejected because they are being blocked by IP-based spam filters. I wrote to my hosting company and their suggestion is that she use her ISP's SMTP server instead of smtp.herdomain.com .

Is that a reasonable request? {She is totally a non-technical person so changing this on her outlook/iphone/blackberry (yes, BOTH) is going to be a huge hassle that I'd like to avoid.} Do most people use their own/ISP SMTP addresses instead of the ones attached to their domain? I was under the impression that using a not-your-domain SMTP server was actually MORE likely to get you marked as spam.

(Apologies if this is not appropriately "answerable". I'm just not even sure whether this is standard practice or a lame hacky solution by my hosting company. Thanks!)

3 Answers 3


Yes, I believe it is a reasonable request, however it suggests that the hosting service is allowing people to use their SMTP service for SPAM, which is why RBLs are saying her emails are SPAM.
Anyway, as long as her ISP can add her domain to the SPF records on their DNS server, it should not increase the probability that mail from her domain via her ISP's SMTP server will get tagged as SPAM.


There really is no general answer (as you pointed out yourself :-)), but AFAIK it's fairly common to use your ISPs SMTP server for outgoing mail, among other things because many systems will view mail coming from a hosted server with suspicion (i.e. flag it as spam); particularly if it's from a dialup IP (there are even blacklists for that).

That said, one simple solution would be to keep your own SMTP server, and have it forward all outgoing mail to your ISP's SMTP server. That is the common setup for intranets: An SMTP server in the intranet, which delivers internal mail and forwards outgoing mail to the ISP's SMTP server.

I was under the impression that using a not-your-domain SMTP server was actually MORE likely to get you marked as spam.

Hard to say (spam filters vary a lot), but this is quite common, as many home users and small businesses have their own domain and use it in their mail address, but don't have their own server; so they will all send via their ISP (I do that myself).

Another option: Instead of your ISP's SMTP, use your hosting provider's SMTP server (they should also have one), so SMTP server and domain will "match".

  • Concerning the "Another option", that's what her client is already doing... Using the hosting provider SMTP server. BTW, it's SMTP not STMP Jan 6, 2010 at 15:12
  • As to "using the hosting provider's SMTP server": If she's already doing that, then the hoster apparently somehow landed on a blacklist, so she should probably complain to them, as in Scott Lundberg's answer. Or just use her ISP's server.
    – sleske
    Jan 7, 2010 at 16:52

If emails are being blocked by IP based filters, it is possible that

  1. Your IP is on some RBL somewhere
  2. Your Email server needs some additional configuration that other servers expect.

If it is a simple problem of getting your IP off some RBL, your client may be able to continue with current SMTP Server.

To check out what could enable you to continue using your SMTP Server, try this Email Server Test

If you are not able to find any issues reported by this test (or) you are unable to carry out the technical changes suggested, the best option would be to use the ISP's SMTP Server.

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