What are punctuation marks omitted in opening and closing lines of a letter the style is called?

The style of omitting punctuation marks in the opening and closing lines of a letter is called open punctuation.

This style is considered more informal and is often used in personal letters or emails. It can also be used in business correspondence, but it's important to be aware of the company's preferred style.

Here's an example of open punctuation:

Dear John,

I hope this email finds you well.

Sincerely,

Jane

Here's the same letter with closed punctuation:

Dear John,

I hope this email finds you well.

Sincerely,

Jane.