Can I set a custom/alpha tag (from number) for email to SMS?
Yes, you can use any number or name you like when sending an SMS using email to SMS. Simply edit/add the allowed email to SMS address and set the Sender Number.
If you've purchased a dedicated number, you can set this as the Sender Number too.
You can edit the settings here:
https://dashboard.clicksend.com/#/sms/settings/sms-allowed-addresses