Quick answer
Send from a name your guests recognise, put the occasion and the date in the subject line, lead with one sentence saying what and when, and give exactly one prominent link. Save the detail for the event page.
The sender name does more work than the subject
People open mail from people. "Amara and Tom" is opened; "Events Team" is scanned; an unfamiliar brand name is ignored. Whatever platform you use, make sure the from-name is yours rather than the software's.
Subject lines: be specific, not clever
An invitation subject line has one job: make the contents unmistakable in a crowded inbox.
- You're invited: Amara & Tom's wedding, 14 June
- Save the date — Priya's 40th, Saturday 8 March
- Company summer party: 3 July, RSVP by 20 June
- Ravi's christening — details and RSVP inside
Each contains the occasion and a date. None of them requires the reader to open the email to work out what it is.
The first line is a second subject line
Most mail apps show a preview. Do not waste it on "We are so excited to share some news" — put the what, where and when in that first sentence, and let the excitement follow it.
One link, one action
A guest reading on a phone should see a single obvious button. Directions, schedule, dress code, registry and accommodation all belong on the event page behind it — an email with six links is an email where the RSVP button competes with five distractions.
Length: shorter than you think
Four short paragraphs is plenty. The email exists to get someone to the page; the page exists to answer everything else. If your invitation email needs scrolling on a phone, some of it belongs on the page.
When to send
Mid-week mornings tend to be read more carefully than Friday afternoons, but the honest answer is that timing matters far less than clarity and follow-up. Do not delay a send by a week to chase an optimal hour.
Personalise the one thing that matters
Names, not adjectives. "Hi Ruth" and, where it applies, "we have reserved seats for you and Michael" do more than any amount of warm language, because they prove the invitation was meant for that person specifically. When each guest has their own invitation record, that personalisation is automatic rather than a mail-merge you have to check by hand.