In reply to a post by RobertoS:

Anyone care to enlighten me as to their advantages? And disadvantages.

Sure.

Some people are geeks and like to do stuff this this.

Privacy. If you use Gmail then Google potentially can read your mail. Might be a reason for the paranoid, but paranoia isn't illegal.

In reply to a post by camieabz:

Privacy, reliability, security.

Meaningless, unless you explain in what way. All three, in my ignorance hence the question, I would almost certainly class as weaknesses of in-house.

In reply to a post by AEP:

I suspect that if static addresses become more common, and are misused in the same way then static address ranges will also be blacklisted (many already are).

Indeed. But blacklist removal procedures exist, and provided the owner of the static IP address can keep it "clean", it will stay removed from blacklists.

How much work is needed to make the mail server work if the IP address changes?

It should be automatic; just a question of waiting for a DNS change to propogate; probably in the region of 24 hours maximum for the average TTL. If it's likely to be a problem you would make the TTL for your mail server's DNS record shorter. When I've had to change the (static) IP address of enterprise mail servers the change has not been a big deal. Bear in mind that most remote web servers won't have the address cached anyway.

In reply to a post by Oliver341:

Privacy. If you use Gmail then Google potentially can read your mail. Might be a reason for the paranoid, but paranoia isn't illegal.

I too am paranoid about google. I would not under any circumstances entrust my normal email to them or Hotmail or Yahoo. I don't really see that as answering the question.

Though its relevance to what MrSaffron said could be high. I wonder what proportion of the 19 million use those three, plus BT and I assume TT ISP email.

failed or slow DNS updates can lead to mail being sent to the wrong IP address

No. For starters, it's unlikely that the new host with that address will be running an SMTP server. And, if it is, it won't be accepting mail for your domain. At worst it will bounce the mail and the remote server should try again after an interval.

In reply to a post by AEP:

No. For starters, it's unlikely that the new host with that address will be running an SMTP server. And, if it is, it won't be accepting mail for your domain. At worst it will bounce the mail and the remote server should try again after an interval.

A static IP address sounds preferable to me.

Some ISP's use a large IP block and hand out individual IP addresses statically from this

A difference between a static block registered to a person/connection and a static IP served to a connection from a larger pool

Oh, I agree with you there. That's why I have a static IP address.

In reply to a post by AEP:

It should be automatic; just a question of waiting for a DNS change to propogate; probably in the region of 24 hours maximum for the average TTL. If it's likely to be a problem you would make the TTL for your mail server's DNS record shorter. When I've had to change the (static) IP address of enterprise mail servers the change has not been a big deal. Bear in mind that most remote web servers won't have the address cached anyway.

Fair enough. Though I'm very hazy about how long sending servers will retry, and what happens if the address is in use elsewhere in the meantime?

Commercial servers have fail-over provision to store incoming mail don't they? So they must feel it is necessary to cater for server failure or connection loss. And they aren't on dynamic IPs.