AIBU to tell you all that I have, today, received a

[GinUser]

wedding invitation complete with poem that does not scan!
To add insult to injury the invitation was addressed to Ms GinUser Maiden Name when I am Mrs. GinUser Married Name.
And there was over-enthusiastic use of the word "gift" where I would use present.
However, you will all be pleased to know that I have already sent my RSVP to the dedicated e-mail address and did not have any dietary requirements :-)

I hope you're not going, Gin, these people clearly have no class.

You have to share the poem! (Edited to protect the money grabbers innocent )

what does a poem that does not scan mean?

Well, to be fair, the poem is a standard job from a company that provides certain services, but even so.
I do not really have much choice in whether I go or not, probably only death would be an acceptable excuse. I mean I even got a Save the Date card (my first, too)!
I am just rather sad that it is all so tasteless and complicated these days.
I have already exchanged 4 e-mails with the venue this afternoon about staying there (as instructed). Quite clearly they are only able to accommodate guests staying after the wedding rather than beforehand (which I need as I will be travelling a fair distance to attend).
When my friends got married it was all so much more simple. Invitation not too far in advance, wedding list, no poems, guests sorted their own accommodation.

I don't understand your post OP?

A poem scans if the syllables fit the metre.

eg

There was a young lady of Harrow.
Who complained that her cunt was too narrow,
For times without number
She would use a cucumber,
But could not accomplish a marrow.

It does not scan if the syllables don't fit the pattern, either because the stresses are in the wrong places, or because too many/few syllables are being shoehorned in.

There was a young man from Japan,
Whose limericks just wouldn't scan,
When he was asked why,
He said in reply,
"I'm not really sure but I think it might be because I always try to cram as many words into the last line as I possibly can".

What's the poem?

en.wikipedia.org/wiki/Scansion

And the latest mail informs me that I can only check in 90 minutes after the actual wedding time.
Death is beginning to seem quite attractive!

ugh... clearly the sort of venue that has a conveyor belt approach to weddings...

Booked in for the day before as well, so that is sorted. People very pleasant and helpful, but clearly not used to dealing with guests from abroad with "requirements".
Now all I need to do is decide what to wear. Silk jumpsuit or silk shirt and trousers. I have everything available. Jumpsuit (Temperley) will need to be taken in, ditto trousers, but least of my problems today.

Are your trousers/jumpsuit white or cream?

Shirt and trousers no white or cream, jumpsuit is the Temperley Heron, blue with cream, but little cream. I would wear with blue shoes and have a blue bag.
Or should I just turn up in my wedding dress? LOL!