$ grep X-Mailer INBOX |sort|uniq -c|sort -r > /var/tmp/xmailer.txt🆑
$ head -n 15 /var/tmp/xmailer.txt🆑
    290 X-Mailer: Microsoft Outlook Express 6.00.2900.5512
     73 X-Mailer: Supmailer 38.2.0
     26 X-Mailer: Microsoft Windows Live Mail 16.4.3505.912
     26 X-Mailer: Microsoft Outlook Express 6.00.2900.5931
     19 X-Mailer: Microsoft Outlook 16.0
     19 X-Mailer: Foxmail 7, 0, 1, 91[cn]
     12 X-Mailer: Microsoft Outlook 15.0
     10 X-Mailer: Microsoft Outlook 14.0
      8 X-Mailer: Microsoft Windows Live Mail 15.4.3508.1109
      8 X-Mailer: Microsoft Outlook Express 6.00.2900.2180
      8 X-Mailer: Microsoft Outlook Express 6.00.2800.1106
      6 X-Mailer: Supmailer 37.0.3
      6 X-Mailer: Microsoft Office Outlook 11
      5 X-Mailer: ClickM@iler
      5 	h=From:To:Subject:Date:MIME-Version:X-Mailer:Content-Type;
$

9933 header __XM_MS_IN_GENERAL     X-Mailer =~ /\bMSCRM\b|Microsoft (?:CDO|Outlook|Office Outlook)\b/
9934
9935 header __XM_OL_10_0_4115    X-Mailer =~ /^Microsoft Outlook, Build 10.0.4115$/
9936
9937 header __XM_OL_28001441    X-Mailer =~ /^Microsoft Outlook Express 6.00.2800.1441$/
9938
9939 header __XM_OL_28004682    X-Mailer =~ /^Microsoft Outlook Express 6.00.2800.4682$/
9940
9941 header __XM_OL_48072300    X-Mailer =~ /^Microsoft Outlook Express 5.50.4807.2300$/
9942
9943 header __XM_OL_4_72_2106_4  X-Mailer =~ /^Microsoft Outlook Express 4.72.2106.4$/
9944
9945 header __XM_OUTLOOK_EXPRESS    X-Mailer =~ /^Microsoft Outlook Express \d/
9946
9947 header      __XM_PHPMAILER_FORGED  X-Mailer =~ /PHPMailer\s.*version\D+$/
9948
9949 header     __XM_RANDOM                 X-Mailer =~ /q(?!(?:q|box|i\s)?mail|\d|[-\w]*=+;)[^u]/i
9950
9951 header   __XM_SKYRI             X-Mailer =~ /^SKYRiXgreen/

9945 header __XM_UJP001 X-Mailer =~ /^Microsoft Outlook Express 6.00.$/
9946 header __XM_UJP002 X-Mailer =~ /^Supmailer$/
9947 header __XM_UJP003 X-Mailer =~ /^Microsoft Windows Live Mail$/
9948 header __XM_UJP004 X-Mailer =~ /^Foxmail$/

3960 ##{ SPAMMY_XMAILER
3961
3962 meta SPAMMY_XMAILER (__XM_OL_28001441||__XM_OL_48072300||__XM_OL_28004682||__XM_OL_10_0_4115||__XM_OL_4_72_2106_4)
3963 describe SPAMMY_XMAILER X-Mailer string is common in spam and not in ham
3964 ##} SPAMMY_XMAILER
3965

3962 meta SPAMMY_XMAILER (__XM_UJP001||__XM_UJP002||__XM_UJP003||__XM_UJP04||__XM_OL_28001441||__XM_OL_48072300|
     |__XM_OL_28004682||__XM_OL_10_0_4115||__XM_OL_4_72_2106_4)
3963 describe SPAMMY_XMAILER X-Mailer string is common in spam and not in ham
3964 ##} SPAMMY_XMAILER