4 ms·

I don't know much about email, but how would some random service send an email from my domain if I've never given it any auth tokens?

jraph 9mo ago
It should not, but it's usual to configure random services to send mails to users, for instance for password resets, or for random notifications. Another thing usually sending mails is cron, but that should only go to the admin(s). Some services might also display the host name somewhere in their UI.
TheDong 9mo ago
You don't need any auth to send an email from your domain, or in fact from any domain. Just set whatever `From` you want. I've received many emails from `root@localhost` over the years. Admittedly, most residential ISPs block all SMTP traffic, and other email servers are likely to drop it or mark it as spam, but there's no strict requirement for auth.
- prmoustache 9mo ago
  > Admittedly, most residential ISPs block all SMTP traffic, and other email servers are likely to drop it or mark it as spam, but there's no strict requirement for auth. Source? I've never seen that. Nobody could use their email provider of choice if that was the case.
  - namibj 9mo ago
    They don't do DPI, they just look at the destination port. And that's why there's a separate port for submission to mail agents where such auth is expected and thus only outbound mail is typically even attempted to be submitted to. Technically local delivery mail too, e.g. where the From and the To headers are valid and have the same domain.
  - TheDong 9mo ago
    The 3 most common ISPs in the US are Comcast, Spectrum, and AT&T Comcast blocks port 25: https://www.xfinity.com/support/articles/email-port-25-no-longer-supported https://www.xfinity.com/support/articles/email-port-25-no-lo... AT&T says "port 25 may be blocked from customers with dynamically-assigned Internet Protocol addresses", which is the majority of customers https://about.att.com/sites/broadband/network https://about.att.com/sites/broadband/network What ISP are you using that isn't blocking port 25, and have you never had the misfortune of being stuck with comcast or AT&T as your only option?
    - prmoustache 9mo ago
      Well I am not in the USA for a start but if it is blocked it must be only inbound otherwise it would break everybody.
      - jraph 9mo ago
        > if it is blocked it must be only inbound Yep, at least in France it's like this for ISPs doing this IIRC.
- flexagoon 9mo ago
  You can, but most email providers will immediately reject your email or put it into spam because of missing DKIM/DMARC/SPF

jraph 9mo ago

It should not, but it's usual to configure random services to send mails to users, for instance for password resets, or for random notifications. Another thing usually sending mails is cron, but that should only go to the admin(s). Some services might also display the host name somewhere in their UI.

TheDong 9mo ago

You don't need any auth to send an email from your domain, or in fact from any domain. Just set whatever `From` you want. I've received many emails from `root@localhost` over the years. Admittedly, most residential ISPs block all SMTP traffic, and other email servers are likely to drop it or mark it as spam, but there's no strict requirement for auth.

prmoustache 9mo ago
> Admittedly, most residential ISPs block all SMTP traffic, and other email servers are likely to drop it or mark it as spam, but there's no strict requirement for auth. Source? I've never seen that. Nobody could use their email provider of choice if that was the case.
- namibj 9mo ago
  They don't do DPI, they just look at the destination port. And that's why there's a separate port for submission to mail agents where such auth is expected and thus only outbound mail is typically even attempted to be submitted to. Technically local delivery mail too, e.g. where the From and the To headers are valid and have the same domain.
- TheDong 9mo ago
  The 3 most common ISPs in the US are Comcast, Spectrum, and AT&T Comcast blocks port 25: https://www.xfinity.com/support/articles/email-port-25-no-longer-supported https://www.xfinity.com/support/articles/email-port-25-no-lo... AT&T says "port 25 may be blocked from customers with dynamically-assigned Internet Protocol addresses", which is the majority of customers https://about.att.com/sites/broadband/network https://about.att.com/sites/broadband/network What ISP are you using that isn't blocking port 25, and have you never had the misfortune of being stuck with comcast or AT&T as your only option?
  - prmoustache 9mo ago
    Well I am not in the USA for a start but if it is blocked it must be only inbound otherwise it would break everybody.
    - jraph 9mo ago
      > if it is blocked it must be only inbound Yep, at least in France it's like this for ISPs doing this IIRC.
flexagoon 9mo ago
You can, but most email providers will immediately reject your email or put it into spam because of missing DKIM/DMARC/SPF