Photos and other types of attachments can vary in size. Many email systems, including Gmail, Yahoo, and Exchange limit the size of email messages you can send. If you're concerned about the size of your email messages or if you've received a message that your email is too large to send, there are several steps you can take to reduce the size of the attached pictures and other documents. 

Since each message you send is stored in your Sent Items folder, reducing the size of attachments can also help keep your mailbox size small.

 Compress pictures to reduce file size

Compressing a picture maintains the height and width of the picture, but reduces the resolution. Lower resolution pictures have a smaller file size.

1. Select the picture or pictures you need to reduce.
   

2. Under Picture Tools on the Format tab, select Compress Pictures  from the Adjust group. Depending on your screen resolution, you may only see the Compress Pictures icon.
   

3. Select the compression and resolution options and then select OK. For pictures that won't be printed, Web (150 ppi) is the most common resolution.
   

Important: Compressing a picture to reduce the size of the file changes the amount of detail retained in the source picture. This means that after compression, the picture can look different than before it was compressed.