[CentOS] [Off topic] sending mail from Comcast was: Sendmail not working

Sun Apr 19 22:10:31 UTC 2020
Jonathan Billings <billings at negate.org>

On Apr 19, 2020, at 4:15 PM, Jonathan Billings <billings at negate.org> wrote:
>> On Apr 19, 2020, at 3:47 PM, S.Bob <sbob at quadratum-braccas.com> wrote:
>> my relay will be smtp.fastmail.com <http://smtp.fastmail.com/> and it requires authentication and SSL, are there added settings in main.cf that will allow this?
> Yes.  You’ll want to use your favorite search engine to look up "centos postfix relayhost sasl”.  Ignore any of the wiki.centos.org <http://wiki.centos.org/> links, they’re so out of date its embarrassing. (for example, the HowTos/postfix_sasl_relayhost wiki page tells you to use stunnel and an init service downloaded from a bugzilla post!)
> The important thing is you’ll set up smtp_sasl_password_maps to point to a file that has your username and password so it can authenticate against smtp.fastmail.com:587 <http://smtp.fastmail.com:587/>.
> You’ll have to make sure it goes to port 587 — traffic from Comcast customers to external port 25 is blocked.

https://wiki.centos.org/HowTos/postfix_sasl_relayhost <https://wiki.centos.org/HowTos/postfix_sasl_relayhost>

I might have complained too loudly about the wiki site, so now it has somewhat more accurate information.  Please give feedback if it doesn’t work for you.

These changes won’t remove your IP from the spamhaus DNSBL though — that’s something between your ISP and spamhaus.  If you continue to get blocked I suggest you open up a case with your ISP because one of their IPs is being blacklisted and it is preventing you from sending email through their SMTP relay.

Jonathan Billings <billings at negate.org>