You’ve seen it the gobbledy gook on the form that comes to your inbox from your website contact form. There is literally no way to stop this new generation of spam short of introducing a captcha field on your contact form.
A captcha field is one of those auto generated boxes filled with a combination of letters jumbled together. Only people can read them not spam robots, so they defeat the use of your online contact form by robo spammers. One of the biggest issues that real users have with sites that use captcha is that sometimes the letters and numbers are not easily readable and can create problems especially for those that are visually disabled. Case in point is the captcha used on many Google pages. If you can read it let me know. Worse yet is the audio link that tells you what the captcha says. The speaker has a very heavy Indian accent which makes understanding what the letters and number are impossible.
The bottom line is this is you use a contact form on your website, you will probably get robo spam. It is not an issue of a poor web host or a problem with your spam filter, it is simply the new generation of spam that gets to you because it uses your website’s contact form script to send you the spam thereby getting past ISP filters.