In the off chance that the address was good, but the recipient choose to send that response because of your letter, here are some suggestions:

You wrote:
I would like to offer my services as Copy Editor. English is a second language to me and I have published articles and presented papers that have been selected for publication internationally.

Since the project post was for copy editing services, that second sentence would dissuade me from using your services. Grammatically, there should be a comma after “me.” However, I would not even create a compound sentence from those two statements; they aren’t logically connected. And if your prospective client were a nit-picker, she’d prefer “published” be replaced with “written,” since “publication” appears later in the sentence.

I have extensive experience editing corporate reports, papers and publications and have developed a keen eye for grammatical errors and sentence construction. I have also a deep sense of urgency to meet your deadline for the completion of work.

Again, your “keen eye” let you down. Read that first sentence again, pausing for the comma but continuing unabated since there is no other punctuation. At least, insert a comma after “publications.”

I would also insert a comma after papers, although opinion has become divided on the necessity for the serial comma when not absolutely required for clarity. Historically, the serial comma has been standard and was eliminated by the print media to save column space. When in doubt, I go with the historical standard.

If your client is in the US, “have also” will sound strange; we would typically reverse that usage. The remainder of that second sentence also comes across as overly emotional, as if it were a clumsy translation.

Since I have recently retired, I can work on your manuscript full time from home. I have a PayPal account so my location won’t be a problem.

From a marketing perspective, I would drop the mention of your recent retirement — the prospect may want a younger editor. Likewise, at this stage, the client has no concern over how you get paid — that’s your concern. All that last sentence does is introduce a potential problem — what if the employer does not use PayPal?

My resume will be immediately available if required.

Again, this usage is not standard in the US, and it is not accurate. How can your resume be “immediately available” if you have not already sent it before they require it? Change “available” to “provided” and “if required” to “upon request.”

Hope this helps.

I don’t waste my time with the high volume/low-paying gigs. I know some writers can “crank them out” to make it worth their time but that’s just not me. The best thing I did was sign up for LinkedIn and join industry-specific Groups. I am specialized and this has been a real boon to business. I have received a lot of referrals. I am writing more and more now from referred business and less and less from postings. I still respond to postings though because you never know when those gigs might go away-like one website where I submit articles 1x/month that just lost 2 major backers.

Thanks for all you do, Anne. I need to go write now.

I would like to offer my services as Copy Editor. English is a second language to me and I have published articles and presented papers that have been selected for publication internationally.

I have extensive experience editing corporate reports, papers and publications and have developed a keen eye for grammatical errors and sentence construction. I have also a deep sense of urgency to meet your deadline for the completion of work.

Since I have recently retired, I can work on your manuscript full time from home. I have a PayPal account so my location won’t be a problem.

My resume will be immediately available if required.