Q:
Question about code sent to Email
I’m guessing you are talking about buying the expansion through the gem store in game. The serial code was sent to you for your records in the event you need it for support or any other reason. If you pre-ordered and received all the items, then yes your account is upgraded to HoT.
Further reading:
https://help.guildwars2.com/entries/94582027-Heart-of-Thorns-Pre-Purchase-FAQ
Email you get sent says:
“Your serial code(s) are listed below. If any of your purchases are gifts, please include the following instructions along with the serial code(s).
Next Steps
1. Go to register.guildwars2.com
2. Login to your existing account or create a new account
3. Follow the instructions to redeem your serial code(s)
IMPORTANT: Please save your serial code(s) for future reference, since our Customer Support team may ask for them if you need assistance. Game serial codes can only be used once to apply game access to a single account. Item serial codes can only be used once and must be applied to an account that already has game access.
If you have questions or need assistance, please view our FAQ and or contact Customer Support."
Since you already have an account just log in (no need to register) and you will see a download link and an add a code link. Click on the Add a Code Link and then add your code. It will recognize it and send you an email.
Email you get sent says [snip]
Unless you upgrade through the gem store which is what it sounds like the OP is referring to. In that case it auto upgrades and you get an email that says this. See image