Learn English – “I thought I did this, but it turns out I only thought about doing it and then forgot to do it?”

be at cross-purposes

at cross-purposes:

If two or more people are at cross purposes, they do not understand each other because they are talking about different subjects without realizing this: I think we've been talking at cross purposes - I meant next year, not this year.

Catch the wrong pig by the ear

the porcine reference is unlikely to be flattering but might not land you in any trouble if the person is crazy and at cross-purposes the whole time.

The enclosed archive of email correspondence includes all messages and headers, though quoted text from previous messages has been deleted for brevity.

This phrase, in bold font above, is copied from https://en.m.wikipedia.org/wiki/Posting_style

When a message is replied to in e-mail, Internet forums, or Usenet, the original can often be included, or "quoted", in a variety of different posting styles.

The main options are interleaved posting (also called inline replying, in which the different parts of the reply follow the relevant parts of the original post), bottom-posting (in which the reply follows the quote) or top-posting (in which the reply precedes the quoted original message). For each of those options, there is also the issue of whether trimming of the original text is allowed, required or preferred.
[...]
Quoted text from previous messages is usually distinguished in some way from the new (reply) text. [...]

On a side note, trimming such text seems very error prone, especially if there have been interleaved or bottom replies. It could also be misleading if emails are presented out of context and order.