If you just want to delete lines in a file containing a particular string, use the following:

I don't know if you want to check for spaces around the word, start and end of lines etc - if you do you will need to modify the above as all that does is look for the existence of the string H3qqea3ur6p and deletes any lines containing it.

This may be a better description of what you want to do, if you mean "email addresses" when you say mails and you provided a represented sample of lines from each file.

Since you are using the entire line, you want to be left with a file that contains items in file1 that are unique.

The "comm" program prints 3 columns. Files unique to file1, files unique to file 2 and files common to both. The -23 option suppresses the printing of the second and third column.

The "comm" program is one of the programs supplied by the coreutils package so you should have it.
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Another way of doing this is using grep with the -f option combined with the -v option. This would remove lines from one file that contains patterns in a second file.

Sorting file2 isn't necessary here but if there is a lot of repetition `uniq' can eliminate the duplicates to save time.

I cannot see any reason that you cannot delete with grep or sed.
Your pattern H3qqea3ur6p is a simple one.
If you don't need extended regexp or don't know how to use it, you can omit -E switch from grep.

Show us your commands.

use grep -v -f [file_delemail] [file_email] > [file_final]