On Thu, Sep 04, 2008 at 02:01:48PM +1200, Mark Foster wrote:
So in terms of the OP, I don't see why joe-user on a dynamic-IP home connection should need the ability to use port 25 to talk to anywhere but their local ISP SMTP server on a normal basis[1].
Whats a normal basis? My Home ISP won't let me send to more than 200 (or so) email addresses per day. If I used my ISP's email system I would constantly be losing my email service due to hitting the limit. I do the field scheduling for my local town soccer league. [Never volunteer! :-) ] So when I send a few announcements out to coaches, referees and administrators, I hit that limit and get my email shutoff for two days or so. I eventually switched to MailHop at DynDNS (smtp auth) I would have used port 25 but our ISP has begun blocking outbound port 25 nationwide, due to large amount of outbound spam from their customers. :-)
Theyre not doing MX lookups so theyre not going direct to remote MTAs[2]. Regardless of where they got the mail _from_, the outbound mail should be via SMTP to their local SMTP server.[3]
If you separate inbound (pop3) and outbound (smtp) mail delivery in your thinking you can start to make sense of things (from a users perspective). This is always the tack i've taken when trying to educate users about why their email outbound doesn't work when theyre moving from ISP to ISP. (At which point you offer them your authenticated-another-way service, such as 587 with SMTP auth).
[1] Customers with a specific need to do so should have the means to opt-out. I believe most of the ISPs in NZ who block 25-outbound from clients also offer this option.
[2] Customers doing MX lookups are either drones or people with mail servers at home. The former are obviously the target of the block. The latter are likely going to be any one of:
- Blocked by SORBS or similar as a dynamic IP - Running a mail server in breach of AUP - On a fixed IP and (theoretically) capable of securing their system and not being a drone or open mail relay (and being traceable via their ISP).
[3] Note also [2]. Outbound mail is associated with your ISP and their SMTP service. Has nothing to do with inbound mail. Nothing. Nada. Zip.
Or doesn't the rest of the world think like this?
Mark.
PS: It occurs to me that SPF has an influence here, if you're aggressively using it then you should also be offering alternatives to Port 25 SMTP. IMHO.
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