PSA: dots are not ALWAYS ignored by GMail (under specific circumstances)

Posting this as a PSA as it caught me out and is a subtlety of the GMail implementation that people might not fully understand.

TL;DR: dots in your username can cause gmail to reject any emails IF they are the first or last character, or if they are consecutive.

I discovered this when I signed up using my normal address, but put 2 consecutive dots ("..") in the username so I could track it if they sold it to spammers. I didn't receive the welcome emails, and after some testing, discovered that all emails to a multiple-dotted email was being rejected.

However, this is a silent rejection most times; nothing warned me about this. I assumed that when every GMail help post reads "GMail ignores all dots" that it was taken literally. However, this is not technically true. It ignores SINGLE dots not at the beginning or end.

The details are to do with the RFC 5322 specification, which GMail appears to have implemented only bits of: https://gmail-miscellany.blogspot.com/2012/08/wrong-email-gmail-dots-issue.html (scroll down to the nitty gritty section).

So, if you have ever given your gmail address with consecutive dots, or with it as a first/last character, you will never receive emails on it.

I hope this helps some people who might have used multiple dots without knowing GMail will reject them.