How can the layout of an envelope be adjusted in mail merge?

Select the size which ties the envelope, or select the custom for setting the size.

If required, you need to select the font as well as the top and left envelope custom value for the size for setting the size.

The above is for adjusting the layout. And for the mail merge you need to follow these steps:

You need to set up the mailing list first. Then you need to test your envelope layout, From the options choose the envelope options, now you need to start the mail merge, now you need to link your mail document with the mailing list, now you to merge the address block with the envelope.

Explanation:

The answer is self explanatory.