Hello,
I have created an invitation in Illustrator, exported it as a .png file, inserted it into Word -- and hope to send it as a mass-mailing email to an excel-based list of email addresses.

I need some help on
(1) whether, in general, this is the right way to proceed
(2) whether .png is the correct choice of file type
(2) what the dimensions of the illustrator invitation should be
(3) whether mail merge will size the invitation for various devices - cell phone to monitor
(4) If there are better options.

I tried a few trials and found that Word stalled/locked. But I'm not sure if this relates to the plan or to something unrelated.
Thank you for any help here! I need it!