your email is not valid

Your system is wrong, my email is valid!

When you register an account on a website, many refuse perfectly valid emails, denying you the possibility to use email aliases or your new fancy username@domain.coffee email.

Possible issues

'New' TLDs

With the increase of top-level domains (as of April 2018, the root domain contains 1543 top-level domains) some websites did not keep up, and won't accept your fancy email ending in @domain.coffee or @domain.xyz despite being perfectly valid

Aliases/Subaddressing

Some mail services support aliases (e.g. yourname+shopping@example.com) where from your email account (yourname@example.com) you append a delimiter (here +) and a tag of your choice (here shopping)

Emails sent to yourname+shopping@example.com will be delivered to yourname@example.com

The tag is up to you, and can be whatever you want to uniquely identify the purpose of an alias.

The advantages are:

Ease email filtering based on the recipient (yourname+school@example.com -> school folder, yourname+tag1@example.com -> tag1 folder, ...)
Tracking the source of spams (spam sent to yourname+website1@example.com -> very likely that something shaddy happened with website1)
Creation of unique, disposable addresses

Some mail services support this feature (Wikipedia article)[https://en.wikipedia.org/wiki/Email_address#Subaddressing]:

Gmail Support page
Rackspace
Yahoo
Apple
Outlook.com
ProtonMail
FastMail
...

If you handle your own email server/domain this is very likely to work out of the box, depending on your MTA configuration though.

Root cause

Validating the format of an email is a difficult known problem, and often syntactically correct emails are rejected.

One workaround if you host your own email service is to change the delimiter to something more likely to be accepted (with Postfix I changed the recipient_delimiter) to -, it works pretty well.

Otherwise, contacting the website customer support is the only way to get this fixed.

Proposition

While an isolated complain to the customer support is unlikely to change things, I would like to list here all the websites not accepting email aliases.

I don't mean to publicly shame them (as they may not even be aware of the issue), but to raise awareness about the pain, get them to eventually fix their system and vent your spleen :)

Contributions

Websites

Please create a pull request with the following information:

Website url
When you tried to register
The format of the email refused
Eventually, a screenshot of the relevant part of the form (please don't use your email address, but something that matches the reject format like name+tag@example.com)

Okay, how should I check the email then?

As I am not a web developer, I have no clue about the possible best solutions to address this problem. If you have experience on this matter, I would be very happy if you can share your experience.

Thank you for trying to make Internet a bit less annoying place :)

Websites refusing valid emails

bouyguestelecom.fr

2019/03/30 During sign up an email with a + character is accepted, but later not accepted by the sign in form, making follow-up of the subscription process impossible. This is only during the subscription process. Feedback