2. Beware of scams (Spam/Phishing).
When dealing with a particular company or product that requires account information, you've probably seen this message: "Never give out your personal information. We will never ask you for your password. "When someone sends you an email asking for your personal information, you immediately know it's a trick - Spam.
But there's another layer to this scam and it's called phishing. Basically, the malicious users mimic high profile sites (e.g. eBay, Amazon, Facebook, etc.) and will let you know that your account is experiencing problems. All you have to do to fix this problem is to send them your username and password to verify your authenticity. Sometimes they will link you to a fake site that looks exactly like the real one. Be cautious, contact the respective support of the site that has "sent" you that particular email and never give out your details (username/password).
3. Do not click on all links.
Every time you see a link in an email, 99% of the time you shouldn't click on it. The only exceptions are when you're waiting for a specific email, such as a forum registration link or an account activation email.
If you receive a spam email trying to sell you a specific service or product, don't click on any of the links inside. You never know where they will lead you. Sometimes they may be safe. Other times they will bring you face to face with malware and viruses.
If you receive an email from your bank or any other service (e.g. bill payments), always visit the site manually (not through your email).
4. Do not open attachments.
Attachments are a tricky parameter when it comes to email. If you're expecting something from a friend or an acquaintance, then by all means, go ahead and open the attachment.
But if the email is not requested, never open the attachment(s) it contains. Even if the file seems "innocent". File names can be spoofed. JPEG files could be EXEs via renaming/editing and these EXEs will run as soon as they are downloaded and are likely to be malicious.
5. Antivirus / Antimalware check.
If you open an email and it looks suspicious in any way, run an antivirus immediately.
TIP : Run antivirus and also malware scan on your computer at regular intervals. Make sure your Malware/Antivirus scan is upgraded and updated to the latest versions.
6. Check your filters from within your webmail.
Maliciously someone can log into your webmail and through the filters activate a redirect to a third party email account of their own. You should regularly check your filters through your webmail.
In case you use Horde -> Preferences -> Filters.
In case you use Roundcube -> Settings -> Filters.
7. Use ports with Encryption.
If you have installed your email in a mail client such as Outlook, for example, in the outgoing mail port, specify ports that use encryption such as 465 with SSL or 587 with TLS/SSL.