Is the message safe to be delivered – Checking the content ?
ISP’s go a step further and even check the contentmailing address example philippines of the email and then finally it allows a particular email to be get delivered in the inbox of the recipient.
Malicious embeds – Many times hackers implant viruses in a legitimate looking mail, this affects the recipient subscriber by taking control of the system and sharing the confidential things like passwords etc. Hackers widely use such techniques as online advertisers use significant efforts to attract users to sell or advertise the products.

Check spam words and phrases – each and every word of the mail is checked to know if there is any spam word or a phrase in the email content.
Link to word ratio – This is also very important criteria. As the mailer should not only have links as such kind of things are identified as spam by the ISP’s. That’s why a good email marketer keeps a mix of text and links.
Text to Image ratio – The mail body should not only contain images, the acceptable ratio between text to image is 70:30
As discussed previously email deliverability is one of the key criteria which the marketers can’t ignore. The success of an email campaign is heavily dependent on the above mentioned key aspects. Marketers stand a chance of jeopardising the success of the of the email campaign if they neglect any of the above-mentioned points. Though there can be various other reasons as well which can impact the mail delivery. Like even if the marketer after clearing all the above checkpoints manager to hit the inbox of the subscriber or recipient, Service providers have given the final authority to the recipient who can still choose to ignore any email and mark it as a spam. Though those reasons can be attributed to the design, layout, fonts used offers displayed overall the look and feel of an email. Such things can be managed and can be worked upon to get a better result.