Since day one, I have received many e-mail letters from so-called "SEO experts" which offered to me search-engine optimization; more content on my website; trying to convince me that my website is missing visitors and followers on social media, so they are offering ways to attract more visitors and generate followers for me on Facebook and/or Google+, etc. So far through the years, there have been many fake and spam SEO offers. Their fishing has changed a bit for the time being, but there are still ways to recognize the spam. Here are examples from my own experience on this matter:
1) The e-mail address of the "SEO-experts" is either some combination of letters that is unpronounceable (something which no reputable company will do), or the e-mail domain is one of the main mailing service providers (Gmail, Yahoo, etc.). Well, you cannot pretend that your company is more than 20 years within the SEO business, and to use a Gmail account.
2) Their letters usually start with some text that they have found on the internet our website, and at the same time, their pretend they "discovered" that it is not in the preferred results in the search engines. Something like "I came to your website by searching on Google but it was difficult to find as you were not on the front page of search results.".... Which brings the question - how you have found our website by chance then?
3) The second point in the content of these spam letters - they write down that they forward it to "the admin", where they use a standard software to put first in the text boilerplate text, getting the keywords for your website. For example: "This is a message to the Attorney in Sofia | Law Firm | Contacts Bulgaria legal services Lawyer in Sofia admin.". So you can get the clear idea that since I am a lawyer situated in Sofia, these keywords on my website have been used by them to convince me that this letter has been drawn personally to me.
4) Usually, senders of these offers avoid direct phone contact with you "I decided to leave a message here on your contact page, instead of calling you...". Fake and spam letters never include a direct contact back.
5) The spam SEO offers direct you to some website with unfamiliar and very often, unpronounceable name, where they pretend, they have a lot of traffic. A website which never relates to the sender's e-mail address, by the way. Yeah, right. Of they offer you something like "Increase your followers in only hours with our powerful social media offers. Visit our website......". Or they may offer "site ranking booster package". There are some offers of the type "freelancer writer is needed".
Mostly these are generated in bulk by a software tool or program. And the main goal of these spam letters with offers is just to make you click on the listed web addresses, so to help them generate traffic to it. This is called "fishing".
6) Another clue that you are a target of spammers is that they never sign their letters and never leave the standard contact details (names, job position, telephone number and e-mail for correspondence), although they pretend to be part of a very professional company in this sphere. And even try to convince you about it, like "over 20 years experience starting my own companies and working for major companies and organizations..."
In all cases please be very suspicious to any SEO offers you may receive via e-mail. Especially if they consist any of the above-listed content. Do not answer to these especially to unsolicited offers. Usually, spammers collect your data so they can sell it to real SEO company, which to start then chasing you with their offers. And I have noted that same offers came from multiple senders within a short period. This should ring the bell for you.
Also you can always do an easy check online with part of the text of the emailed offer, in order to see if it has been included already in one of the scam warning websites.
* The above article shares only my personal statement, based only on my personal experience.