Shared hosting has always been a popular choice for hosting a small website with POP email service. It is inexpensive and will usually provide everything you will need. However, one of my clients encountered some problems with their email shared hosting. The issue is with the proliferation of spam, ISPs are banning emails sent from known offenders based on their IP addresses. Since you are sharing a server with many other users, if they spam but your ISP does not catch on, the IP address used will be banned by other ISPs. This would render your email server ineffective as some emails will be filtered out as spam by other ISPs even though they are legitimate emails.
Therefore, it is very important to choose your ISP wisely. A good ISP should be on top of monitoring spam and resolve the problem quickly if they are on the blacklist.