Under some circumstances, you may experience an invalid user error, and this is usually related to the email address provided when creating your Bananatag account.
Before continuing, try logging in to your Bananatag account and make sure that the email you've used as your account login is the same as the one you wish to use for tracking within your mail client.
Some email addresses created in Gmail (especially older addresses or those created outside North America) may not actually be @gmail.com addresses, and may be another variation, @googlemail.com.
Although you can log in using @gmail.com, your account will still sees itself as an @googlemail.com account, which is what will be sent to the Bananatag servers that are attempting to track your emails, and what should be registered in your Bananatag account.
Still experiencing an issue?
If you are still experiencing this issue, please send an email to firstname.lastname@example.org and we will be happy to help.