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n5bb · 4 Jul 2017, 07:28 AM

Yes, that's where there will be more and more problems in the future, Ellen.

If you own a domain, you will be able to specify exactly which SMTP servers are allowed to send for your domain. The way you do this is with DMARC and SPF records in the DNS of the domain you control, and appropriate use of DKIM in the SMTP servers you use for your domain. You can choose to not do this, but eventually as more and more domains use DMARC your domain might be viewed as encouraging spammers.
If you don't own a domain (you are just a user of Gmail, Yahoo, Fastmail, or some other email service), you will have to follow the policy of the owner of the domain. For Gmail and Yahoo, you need to use their outgoing SMTP servers already or you may have some difficulties.

It's not just Fastmail wanting to be sure you have a Gmail account, it's Gmail not allowing anyone to send with a Gmail From address unless it's through the Gmail SMTP server. This is how SPF, DKIM, and DMARC work -- they allow Gmail (or any owner of a domain) to specify that only certain SMTP servers are allowed to send messages for that domain. I'm using Gmail as an example, but this applies to any domain which publishes a DMARC policy.

At this time, Fastmail doesn't publish a restrictive DMARC policy for their domains. But this will probably eventually change.
https://blog.fastmail.com/2016/12/24/spf-dkim-dmarc/

Bill

4 Jul 2017, 07:28 AM	#542
n5bb Intergalactic Postmaster Join Date: May 2004 Location: Irving, Texas Posts: 8,929	Yes, that's where there will be more and more problems in the future, Ellen. If you own a domain, you will be able to specify exactly which SMTP servers are allowed to send for your domain. The way you do this is with DMARC and SPF records in the DNS of the domain you control, and appropriate use of DKIM in the SMTP servers you use for your domain. You can choose to not do this, but eventually as more and more domains use DMARC your domain might be viewed as encouraging spammers. If you don't own a domain (you are just a user of Gmail, Yahoo, Fastmail, or some other email service), you will have to follow the policy of the owner of the domain. For Gmail and Yahoo, you need to use their outgoing SMTP servers already or you may have some difficulties. It's not just Fastmail wanting to be sure you have a Gmail account, it's Gmail not allowing anyone to send with a Gmail From address unless it's through the Gmail SMTP server. This is how SPF, DKIM, and DMARC work -- they allow Gmail (or any owner of a domain) to specify that only certain SMTP servers are allowed to send messages for that domain. I'm using Gmail as an example, but this applies to any domain which publishes a DMARC policy. At this time, Fastmail doesn't publish a restrictive DMARC policy for their domains. But this will probably eventually change. https://blog.fastmail.com/2016/12/24/spf-dkim-dmarc/ Bill Last edited by n5bb : 4 Jul 2017 at 07:36 AM.