I have some @which.net email addresses. They have recently changed to using SSL for incoming mail. However they don't have a smtp server. Customers are told the use their ISP smtp server.

which.net publishes an SPF record that lists IP addresses that are trusted, and states other IPs are neutral.

An SPF record allows a receiving ISP to look at the incoming message and decide if it is trusted based on the domain name of the email and what that domain publishes.

Many ISPs in the USA (e.g. verizon.net) would silently ditch the email from you using which.net and sent from say Plusnet's relay server because the IP of Plusnet's server wasn't listed in the SPF record so you fell into the neutral category.

If it matters to you that your email is 90% likely to make it to the recipient, pick an email service that lets you receive and send through them from anywhere, and ensure your mail has a published SPF record. Even better get DKIM enabled.

The old university idea you could sent from any relay server (on the network you were attached to) is dead ; sadly thanks to spammers. But the filtering happens at the recipient, and even paying customers can't get big ISPs to change their email acceptance policy.

I was trying to send email today via relay.plus.net using MSOutlook (Office 2010) on Windows 10. Simply refused to go. I saw this thread yesterday and at first wondered if my problem was related. However I saw that my system had a pending restart and update so I did it manually and that was the problem. Email working again and nothing to do with the server.

Edited by longedge (Wed 12-Apr-17 22:08:22)

Thanks for the info. I must admit most of it went over my head. However I understood the gist of what you said. Where would I find smtp servers which would comply?

In reply to a post by wingco1:

Thanks for the info. I must admit most of it went over my head. However I understood the gist of what you said. Where would I find smtp servers which would comply?

Generally you have to use an SMTP server from the same company that provides your email address. So if your email address is @which.net and you collect mail using POP or IMAP then which.net should provide an SMTP server. If they don't - change your email address to one that does.

The free webmail services (Gmail, Yahoo, Outlook.com) all provide POP/SMTP servers as well ; as do their paid premium equivalents. Web hosting companies also do the same.

Thanks very much.