Backup – Backup to Gmail Failed

I'm using the BackWPup plugin to backup my WordPress site from an Amazon EC2 instance, to my gmail account. I keep getting this error:

ERROR: Job has ended with errors in 25 seconds. You must resolve the
errors for correct execution.

Here are the details of the error (see below). I'm wondering whether my backup is to big for email? If so, would I be charged to use the Amazon S3 service in stead?:

[INFO] BackWPup version 3.0.13; WordPress version 3.6.1; A project of Inpsyde GmbH developed by Daniel Hüsken
[INFO] This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions.
[INFO] Blog url: http://my_domain.com/my_wordpress_dir/ 
[INFO] BackWPup job: WordPress Backup; DBDUMP+FILE+WPPLUGIN
[INFO] BackWPup cron: 0 3 * * 0; Sat, 14 Sep 2013 @ 13:41
[INFO] BackWPup job started manually
[INFO] PHP ver.: 5.3.27; apache2handler; Linux
[INFO] Maximum script execution time is 120 seconds
[INFO] MySQL ver.: 5.5.32
[INFO] curl ver.: 7.27.0; NSS/3.14.0.0 
[INFO] Temp folder is: /var/www/html/my_wordpress_dir/wp-content/uploads/backwpup-f4c53-temp/
[INFO] Logfile folder is: /var/www/html/my_wordpress_dir/wp-content/uploads/backwpup-2d658-logs/
[INFO] Backup type is: archive
[INFO] Backup file is: /var/www/html/my_wordpress_dir/wp-content/uploads/backwpup-f4c53-temp/backwpup_25128c_2013-09-14_13-41-39.tar.gz
[14-Sep-2013 13:41:40] 1. Try to dump database …
[14-Sep-2013 13:41:40] Connected to database mysite on localhost
[14-Sep-2013 13:41:40] Dump database table "some_prefix_3wp_activity_monitor_index"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_3wp_activity_monitor_user_statistics"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_commentmeta"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_comments"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_links"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_login_security_solution_fail"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_options"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_postmeta"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_posts"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_term_relationships"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_term_taxonomy"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_terms"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_usermeta"
[14-Sep-2013 13:41:40] Dump database table "some_prefix_users"
[14-Sep-2013 13:41:40] Added database dump "mysite.sql" with 5.65 MB to backup file list
[14-Sep-2013 13:41:40] Database dump done!
[14-Sep-2013 13:41:40] 1. Trying to make a list of folders to back up …
[14-Sep-2013 13:41:41] 471 folders to back up.
[14-Sep-2013 13:41:41] 1. Trying to generate a file with installed plugin names …
[14-Sep-2013 13:41:41] Added plugin list file "Bob.pluginlist.2013-09-14.txt" with 1.58 kB to backup file list.
[14-Sep-2013 13:41:41] 1. Trying to create backup archive …
[14-Sep-2013 13:41:41] Compression method is TarGz
[14-Sep-2013 13:41:58] Backup archive created.
[14-Sep-2013 13:41:58] Archive size is 16.81 MB.
[14-Sep-2013 13:41:58] 3723 Files with 40.19 MB in Archive.
[14-Sep-2013 13:41:58] 1. Trying to send backup with e-mail…
[14-Sep-2013 13:41:58] Sending e-mail to mygmailaddress@gmail.com…
[14-Sep-2013 13:42:00] ERROR: Error while sending e-mail!
[14-Sep-2013 13:42:00] 2. Trying to send backup with e-mail…
[14-Sep-2013 13:42:00] Sending e-mail to mygmailaddress@gmail.com…
[14-Sep-2013 13:42:02] ERROR: Error while sending e-mail!
[14-Sep-2013 13:42:02] 3. Trying to send backup with e-mail…
[14-Sep-2013 13:42:02] Sending e-mail to mygmailaddress@gmail.com…
[14-Sep-2013 13:42:04] ERROR: Error while sending e-mail!
[14-Sep-2013 13:42:04] Job has ended with errors in 25 seconds. You must resolve the errors for correct execution.