Welcome to the Community, akellman.
I'm here to help and provide you some information about QuickBooks Webmail in QuickBooks Pro 2013.
Right now, QuickBooks Desktop Pro 2013 is no longer supported and all add-on services such as emailing invoices, payroll, online banking, and data services will be discontinued. You might want to consider upgrading your QuickBooks Desktop so you can use this feature.
You can try to download the QuickBooks Desktop trial version, upgrade the file and try to email the invoices again.
These articles are a good reference:
Also, I'd suggest reaching out to your network provider regarding your password.
Should you need more information about emailing invoices, please let me know. I'm here to provide them for you.