I think that's a battle you need to be having with Google. They're the ones misusing the email standards.

Or more likely there's a simple spelling error somewhere where the address is being stored.

In an email address, all characters are equal. Not all punctuation or other special characters are allowed, but those that are, represent a character just the same as any other normal character. So firstnamelastname is NOT the same as firstname.lastname, or firstname_lastname etc. The email servers have no way of 'understanding' what the text means, it is all just a string of ascii characters to them.

At least, that is the standard and the SMTP servers that transmit messages all around the planet have to abide by these rules or it all falls apart.

Then clever dicks come along and try to subvert the standards in their own software by interpreting certain characters to mean special things but it still holds that every character in an email address is important and a single incorrect character (whatever that might be) means it will be considered a different address.

What we also suffer from is bad 'error' checking. Many email clients will no longer accept a simple name/word (i.e. no @) as a valid address. Often not even accepting an address with an @, but without a dot after it. These are all perfectly valid in the original email standards and simply denote local host and local domain respectively, but the ignorance of the modern developers means this is not understood and so the very hand-holding that is supposed to help us, in fact prevents us from doing what the email standards were designed to provide. I'd rather not be subjected to any such supposed assistance, but it's inexcusable when they are assisting you, nay, FORCING you to actually do it wrong, or at least, NOT allowing you to do it right.

Getting a bit off topic there, sorry.