Best Method to offer options to upgrade mailbox capacity

[HSc]

We offer Email with fixed number of mailboxes, each mailbox with a fixed amount of storage. We also offer ability to add mailboxes 

Some clients buy additional storage space per mailbox. What is the best way to set this up? Configurable Option? Addon? Another way?

I have tried both methods, always using hidden option as it's not necessary to show it to the client. Neither seems to work properly for us so perhaps I'm doing it wrong?

Features we require include:

- prorate (is that correct term) to link fee and renewal in line with existing main product renewal. And only charged for time remaining until anniversary (yearly). 
- text field to enter mailbox address (customer may need to buy separate upgrades per mailbox address
- we offer scaled upgrade (1gb, 2gb, 5gb, etc.)  so the client may upgrade further in the future and/or another mailbox needs a different upgrade (hence need for mailbox field) 
- recurring billing

We are not using cPanel or other "off the shelf" control panel, if that matters. 

Any suggestions would be appreciated.

Thanks for looking.

HSc

[Waqas Ahmed Waseer]

@HSc I'd lean toward product addons rather than configurable options for this, mainly because of your three requirements.

Configurable options fold into the product's price as one line item and share its billing cycle. The types are Dropdown, Radio, Yes/No and Quantity. None of them is free text, so you can't store a mailbox address in one. That's likely why hiding them still felt wrong. You'd need a separate custom field on the product, and one option doesn't map well to "several mailboxes, each upgraded differently."

Addons are billed as separate items, and they cover all three of your needs:

1. Create a Recurring addon. For sizes, either make one addon per tier (1GB, 2GB, 5GB), or one addon priced per 1GB with Allow Multiple Quantities turned on, so quantity equals GB. Separate tiers are easier for clients to read. The quantity route is simpler if your pricing is linear.

2. Turn on Prorata Billing for the addon. It syncs the addon's due date to the parent service, using the parent's prorata settings. That gives you the yearly anniversary alignment.

3. Add a required text Custom Field to the addon, something like "Mailbox address". Each purchase then names the mailbox it applies to.

4. Assign the addon to your email product. Clients can order it under Available Addons, or staff can add it. Do one addon instance per mailbox upgrade.

One caveat, since you're not on cPanel: WHMCS won't resize anything on its own. Your module or manual process has to read the addon's custom field and apply the quota. If you have a provisioning module, check whether it handles addon events. Otherwise you'll need a small hook or a staff task.

Test the prorata date on a dummy service before going live, so you can confirm the due dates land where you expect.

What are you using on the mail side to set quotas?