[walrus01]

Agreed. Don't use real PII for test environments. If you absolutely need to, find a way to create several hundred real functioning email addresses which are dedicated to testing purposes at different domains/services, as widely spread out as you can, to verify that your outgoing email is actually being delivered from a test environment.

You need to be able to verify, by looking at the receive headers on the individual email accounts, from a widely disparate set of receiving SMTP daemons/services that your emails are passing SPF, DKIM, DMARC checks, your IP block is not in some peoples' RBLs, etc.

[simcop2387]

This is why I love Google's feature of letting you generate addresses with a +. It's so very useful

[extra88]

Sub-addressing of the format username+foo@host pre-dates Gmail. I think what is unique to them is being able to include periods anywhere within the username, e.g. us.ern.ame@host, user..nam.e@host, username@host are all equivalent.

https://en.wikipedia.org/wiki/Email_address#Sub-addressing

[walrus01]

which is useful for testing delivery to gmail, but ideally you want to have a really mixed bag of receiving smtp daemons with different spam/abuse filtering profiles (all of which are pretty much opaque these days for anti spam reasons) and different services to test reliable delivery.