Write a re-engagement email

I work in marketing at an accountancy firm. Help me write an email to past clients we have not heard from.

Context: Past clients drift to a cheaper provider or try doing their own return, and often come back when a business grows, a property is sold or a letter from HMRC arrives.

Before you start, ask me for anything missing from this list:
- Who these people are and when we last worked with them
- A real reason to get in touch now
- What we would like them to do

Then:
1. Open with the reason for writing.
2. Offer something useful that asks nothing of them.
3. Make one small ask.
4. Make it easy to say no or to stop hearing from us.

Give me:
- Two versions with different openings
- Subject lines for each

Rules:
- Use only the facts I give you. Where something is missing, write [detail needed]. Never invent a number, a name, a quote or a source.
- Give general information only. Never write anything that reads as tax advice on a person's own affairs, and never suggest a tax saving or an outcome with HMRC is likely or guaranteed.
- Write in plain English, in our voice if I have given you a sample.
- Do not tell me what the rules or regulations say. If something may be restricted, flag it and I will check.

Finish with a list headed "Check before this goes out". Include these, plus anything else the partner who approves marketing or our ethics and compliance lead should see:
- That these people agreed to hear from us
- Any mention of their past affairs, even indirectly
- Offers or fixed fees quoted, and what they include