How to send transactional mails from many addresses (without spamming or on behalf of)

Question

In a Laravel/Symfony SaaS app I want my clients to send out mails to their customers – my clients can manage their customer information in my app.

I am looking for a way they can send emails that are from their own addresses – and not from my domain (via sendmail).

These mails should not have a on behalf of in their FROM, but also I want to make sure that my service will not get gamed by spammers.

One idea was that every client can set up her own SMTP settings which Swiftmailer will then use to deliver the mails for each individual address. Maximum daily delivery per client should by below 500, so that might work.

Another idea was to use a service such as Amazon SES, who let you verify up to 1000 addresses. Or Sendgrid, who offer something similar.

What is the most secure way to send mails from different addresses with a maximized deliverability and minimum risk of being gamed by spammers?

Answer 1

For safe guarding against being marked as spam you need to

1. Have your DKIM and SPF settings in place
2. Do a LITMUS spam test of your email to check your spam score against various spam check engines
3. Do domain throttling

It has nothing to do with email verification in SES because that is just a mandate for using a From email id while sending out emails